
 
mT5
	
Overview
	
The mT5 model was presented in mT5: A massively multilingual pre-trained text-to-text transformer by Linting Xue, Noah Constant, Adam Roberts, Mihir Kale, Rami Al-Rfou, Aditya
Siddhant, Aditya Barua, Colin Raffel.
The abstract from the paper is the following:
The recent “Text-to-Text Transfer Transformer” (T5) leveraged a unified text-to-text format and scale to attain
state-of-the-art results on a wide variety of English-language NLP tasks. In this paper, we introduce mT5, a
multilingual variant of T5 that was pre-trained on a new Common Crawl-based dataset covering 101 languages. We detail
the design and modified training of mT5 and demonstrate its state-of-the-art performance on many multilingual
benchmarks. We also describe a simple technique to prevent “accidental translation” in the zero-shot setting, where a
generative model chooses to (partially) translate its prediction into the wrong language. All of the code and model
checkpoints used in this work are publicly available.
Note: mT5 was only pre-trained on mC4 excluding any supervised training.
Therefore, this model has to be fine-tuned before it is usable on a downstream task, unlike the original T5 model.
Since mT5 was pre-trained unsupervisedly, there’s no real advantage to using a task prefix during single-task
fine-tuning. If you are doing multi-task fine-tuning, you should use a prefix.
Google has released the following variants:
google/mt5-small
google/mt5-base
google/mt5-large
google/mt5-xl
google/mt5-xxl.
This model was contributed by patrickvonplaten. The original code can be
found here.
Documentation resources
	
Translation task guide
Summarization task guide
MT5Config
	
class transformers.MT5Config
<
source
>
(
vocab_size = 250112
d_model = 512
d_kv = 64
d_ff = 1024
num_layers = 8
num_decoder_layers = None
num_heads = 6
relative_attention_num_buckets = 32
relative_attention_max_distance = 128
dropout_rate = 0.1
layer_norm_epsilon = 1e-06
initializer_factor = 1.0
feed_forward_proj = 'gated-gelu'
is_encoder_decoder = True
use_cache = True
tokenizer_class = 'T5Tokenizer'
tie_word_embeddings = False
pad_token_id = 0
eos_token_id = 1
decoder_start_token_id = 0
**kwargs
)
Parameters 
vocab_size (int, optional, defaults to 250112) —
Vocabulary size of the T5 model. Defines the number of different tokens that can be represented by the
inputs_ids passed when calling T5Model or TFT5Model.
d_model (int, optional, defaults to 512) —
Size of the encoder layers and the pooler layer.
d_kv (int, optional, defaults to 64) —
Size of the key, query, value projections per attention head. d_kv has to be equal to d_model // num_heads.
d_ff (int, optional, defaults to 1024) —
Size of the intermediate feed forward layer in each T5Block.
num_layers (int, optional, defaults to 8) —
Number of hidden layers in the Transformer encoder.
num_decoder_layers (int, optional) —
Number of hidden layers in the Transformer decoder. Will use the same value as num_layers if not set.
num_heads (int, optional, defaults to 6) —
Number of attention heads for each attention layer in the Transformer encoder.
relative_attention_num_buckets (int, optional, defaults to 32) —
The number of buckets to use for each attention layer.
relative_attention_max_distance (int, optional, defaults to 128) —
The maximum distance of the longer sequences for the bucket separation.
dropout_rate (float, optional, defaults to 0.1) —
The ratio for all dropout layers.
layer_norm_eps (float, optional, defaults to 1e-6) —
The epsilon used by the layer normalization layers.
initializer_factor (float, optional, defaults to 1) —
A factor for initializing all weight matrices (should be kept to 1, used internally for initialization
testing).
feed_forward_proj (string, optional, defaults to "gated-gelu") —
Type of feed forward layer to be used. Should be one of "relu" or "gated-gelu".
use_cache (bool, optional, defaults to True) —
Whether or not the model should return the last key/values attentions (not used by all models).
This is the configuration class to store the configuration of a MT5Model or a TFMT5Model. It is used to
instantiate a mT5 model according to the specified arguments, defining the model architecture. Instantiating a
configuration with the defaults will yield a similar configuration to that of the mT5
google/mt5-small architecture.
Configuration objects inherit from PretrainedConfig and can be used to control the model outputs. Read the
documentation from PretrainedConfig for more information.
MT5Tokenizer
	
class transformers.T5Tokenizer
<
source
>
(
vocab_file
eos_token = '</s>'
unk_token = '<unk>'
pad_token = '<pad>'
extra_ids = 100
additional_special_tokens = None
sp_model_kwargs: typing.Union[typing.Dict[str, typing.Any], NoneType] = None
legacy = True
**kwargs
)
Parameters 
vocab_file (str) —
SentencePiece file (generally has a .spm extension) that
contains the vocabulary necessary to instantiate a tokenizer.
eos_token (str, optional, defaults to "</s>") —
The end of sequence token.
When building a sequence using special tokens, this is not the token that is used for the end of sequence.
The token used is the sep_token.
unk_token (str, optional, defaults to "<unk>") —
The unknown token. A token that is not in the vocabulary cannot be converted to an ID and is set to be this
token instead.
pad_token (str, optional, defaults to "<pad>") —
The token used for padding, for example when batching sequences of different lengths.
extra_ids (int, optional, defaults to 100) —
Add a number of extra ids added to the vocabulary for use as sentinels. These tokens are
accessible as “id{%d}>” where ”{%d}” is a number between 0 and extra_ids-1. These tokens can be
retrieved by calling get_sentinel_tokens method and token ids can be by calling get_sentinel_token_ids
method
additional_special_tokens (List[str], optional):
Additional special tokens used by the tokenizer.
sp_model_kwargs (dict, optional) —
Will be passed to the SentencePieceProcessor.__init__() method. The Python wrapper for
SentencePiece can be used, among other things,
to set:
enable_sampling: Enable subword regularization.
nbest_size: Sampling parameters for unigram. Invalid for BPE-Dropout.
nbest_size = {0,1}: No sampling is performed.
nbest_size > 1: samples from the nbest_size results.
nbest_size < 0: assuming that nbest_size is infinite and samples from the all hypothesis (lattice)
using forward-filtering-and-backward-sampling algorithm.
alpha: Smoothing parameter for unigram sampling, and dropout probability of merge operations for
BPE-dropout.
legacy (bool, optional, defaults to True) —
Whether or not the legacy behaviour of the tokenizer should be used. Legacy is before the merge of #24622
which includes fixes to properly handle tokens that appear after special tokens. A simple example:
legacy=True:
Construct a T5 tokenizer. Based on SentencePiece.
This tokenizer inherits from PreTrainedTokenizer which contains most of the main methods. Users should refer to
this superclass for more information regarding those methods.
build_inputs_with_special_tokens
<
source
>
(
token_ids_0: typing.List[int]
token_ids_1: typing.Optional[typing.List[int]] = None
)
→
List[int]
Parameters 
token_ids_0 (List[int]) —
List of IDs to which the special tokens will be added.
token_ids_1 (List[int], optional) —
Optional second list of IDs for sequence pairs.
Returns
List[int]
List of input IDs with the appropriate special tokens.
Build model inputs from a sequence or a pair of sequence for sequence classification tasks by concatenating and
adding special tokens. A sequence has the following format:
single sequence: X </s>
pair of sequences: A </s> B </s>
convert_tokens_to_string
<
source
>
(
tokens
)
Converts a sequence of tokens (string) in a single string.
create_token_type_ids_from_sequences
<
source
>
(
token_ids_0: typing.List[int]
token_ids_1: typing.Optional[typing.List[int]] = None
)
→
List[int]
Parameters 
token_ids_0 (List[int]) —
List of IDs.
token_ids_1 (List[int], optional) —
Optional second list of IDs for sequence pairs.
Returns
List[int]
List of zeros.
Create a mask from the two sequences passed to be used in a sequence-pair classification task. T5 does not make
use of token type ids, therefore a list of zeros is returned.
get_special_tokens_mask
<
source
>
(
token_ids_0: typing.List[int]
token_ids_1: typing.Optional[typing.List[int]] = None
already_has_special_tokens: bool = False
)
→
List[int]
Parameters 
token_ids_0 (List[int]) —
List of IDs.
token_ids_1 (List[int], optional) —
Optional second list of IDs for sequence pairs.
already_has_special_tokens (bool, optional, defaults to False) —
Whether or not the token list is already formatted with special tokens for the model.
Returns
List[int]
A list of integers in the range [0, 1]: 1 for a special token, 0 for a sequence token.
Retrieve sequence ids from a token list that has no special tokens added. This method is called when adding
special tokens using the tokenizer prepare_for_model method.
See T5Tokenizer for all details.
MT5TokenizerFast
	
class transformers.T5TokenizerFast
<
source
>
(
vocab_file = None
tokenizer_file = None
eos_token = '</s>'
unk_token = '<unk>'
pad_token = '<pad>'
extra_ids = 100
additional_special_tokens = None
**kwargs
)
Parameters 
vocab_file (str) —
SentencePiece file (generally has a .spm extension) that
contains the vocabulary necessary to instantiate a tokenizer.
eos_token (str, optional, defaults to "</s>") —
The end of sequence token.
When building a sequence using special tokens, this is not the token that is used for the end of sequence.
The token used is the sep_token.
unk_token (str, optional, defaults to "<unk>") —
The unknown token. A token that is not in the vocabulary cannot be converted to an ID and is set to be this
token instead.
pad_token (str, optional, defaults to "<pad>") —
The token used for padding, for example when batching sequences of different lengths.
extra_ids (int, optional, defaults to 100) —
Add a number of extra ids added to the vocabulary for use as sentinels. These tokens are accessible as
“id{%d}>” where ”{%d}” is a number between 0 and extra_ids-1. These tokens can be retrieved by
calling get_sentinel_tokens method and token ids can be by calling get_sentinel_token_ids method
additional_special_tokens (List[str], optional) —
Additional special tokens used by the tokenizer.
Construct a “fast” T5 tokenizer (backed by HuggingFace’s tokenizers library). Based on
Unigram.
This tokenizer inherits from PreTrainedTokenizerFast which contains most of the main methods. Users should
refer to this superclass for more information regarding those methods.
build_inputs_with_special_tokens
<
source
>
(
token_ids_0: typing.List[int]
token_ids_1: typing.Optional[typing.List[int]] = None
)
→
List[int]
Parameters 
token_ids_0 (List[int]) —
List of IDs to which the special tokens will be added.
token_ids_1 (List[int], optional) —
Optional second list of IDs for sequence pairs.
Returns
List[int]
List of input IDs with the appropriate special tokens.
Build model inputs from a sequence or a pair of sequence for sequence classification tasks by concatenating and
adding special tokens. A sequence has the following format:
single sequence: X </s>
pair of sequences: A </s> B </s>
create_token_type_ids_from_sequences
<
source
>
(
token_ids_0: typing.List[int]
token_ids_1: typing.Optional[typing.List[int]] = None
)
→
List[int]
Parameters 
token_ids_0 (List[int]) —
List of IDs.
token_ids_1 (List[int], optional) —
Optional second list of IDs for sequence pairs.
Returns
List[int]
List of zeros.
Create a mask from the two sequences passed to be used in a sequence-pair classification task. T5 does not make
use of token type ids, therefore a list of zeros is returned.
See T5TokenizerFast for all details.
MT5Model
	
class transformers.MT5Model
<
source
>
(
config: MT5Config
)
Parameters 
config (MT5Config) — Model configuration class with all the parameters of the model.
Initializing with a config file does not load the weights associated with the model, only the
configuration. Check out the from_pretrained() method to load the model weights.
The bare MT5 Model transformer outputting raw hidden-states without any specific head on top.
The MT5 model was proposed in Exploring the Limits of Transfer Learning with a Unified Text-to-Text
Transformer by Colin Raffel, Noam Shazeer, Adam Roberts, Katherine Lee, Sharan
Narang, Michael Matena, Yanqi Zhou, Wei Li, Peter J. Liu. It’s an encoder decoder transformer pre-trained in a
text-to-text denoising generative setting.
This model inherits from PreTrainedModel. Check the superclass documentation for the generic methods the
library implements for all its model (such as downloading or saving, resizing the input embeddings, pruning heads
etc.)
This model is also a PyTorch torch.nn.Module subclass.
Use it as a regular PyTorch Module and refer to the PyTorch documentation for all matter related to general usage
and behavior.
Examples:
	Copied
 from transformers import MT5Model, AutoTokenizer
 model = MT5Model.from_pretrained("google/mt5-small")
 tokenizer = AutoTokenizer.from_pretrained("google/mt5-small")
 article = "UN Offizier sagt, dass weiter verhandelt werden muss in Syrien."
 summary = "Weiter Verhandlung in Syrien."
 inputs = tokenizer(article, return_tensors="pt")
 labels = tokenizer(text_target=summary, return_tensors="pt")
 outputs = model(input_ids=inputs["input_ids"], decoder_input_ids=labels["input_ids"])
 hidden_states = outputs.last_hidden_state
deparallelize
<
source
>
(
)
Moves the model to cpu from a model parallel state.
Example:
	Copied
# On a 4 GPU machine with mt5-xl:
model = MT5ForConditionalGeneration.from_pretrained("Mt5-xl")
device_map = {
    0: [0, 1, 2],
    1: [3, 4, 5, 6, 7, 8, 9],
    2: [10, 11, 12, 13, 14, 15, 16],
    3: [17, 18, 19, 20, 21, 22, 23],
}
model.parallelize(device_map)  # Splits the model across several devices
model.deparallelize()  # Put the model back on cpu and cleans memory by calling torch.cuda.empty_cache()
forward
<
source
>
(
input_ids: typing.Optional[torch.LongTensor] = None
attention_mask: typing.Optional[torch.FloatTensor] = None
decoder_input_ids: typing.Optional[torch.LongTensor] = None
decoder_attention_mask: typing.Optional[torch.BoolTensor] = None
head_mask: typing.Optional[torch.FloatTensor] = None
decoder_head_mask: typing.Optional[torch.FloatTensor] = None
cross_attn_head_mask: typing.Optional[torch.Tensor] = None
encoder_outputs: typing.Optional[typing.Tuple[typing.Tuple[torch.FloatTensor]]] = None
past_key_values: typing.Optional[typing.Tuple[typing.Tuple[torch.FloatTensor]]] = None
inputs_embeds: typing.Optional[torch.Tensor] = None
decoder_inputs_embeds: typing.Optional[torch.Tensor] = None
use_cache: typing.Optional[bool] = None
output_attentions: typing.Optional[bool] = None
output_hidden_states: typing.Optional[bool] = None
return_dict: typing.Optional[bool] = None
)
→
transformers.modeling_outputs.Seq2SeqModelOutput or tuple(torch.FloatTensor)
Parameters 
input_ids (torch.LongTensor of shape (batch_size, sequence_length)) —
Indices of input sequence tokens in the vocabulary. MT5 is a model with relative position embeddings so you
should be able to pad the inputs on both the right and the left.
Indices can be obtained using AutoTokenizer. See PreTrainedTokenizer.encode() and
PreTrainedTokenizer.call() for detail.
What are input IDs?
To know more on how to prepare input_ids for pretraining take a look a MT5 Training.
attention_mask (torch.FloatTensor of shape (batch_size, sequence_length), optional) —
Mask to avoid performing attention on padding token indices. Mask values selected in [0, 1]:
1 for tokens that are not masked,
0 for tokens that are masked.
What are attention masks?
decoder_input_ids (torch.LongTensor of shape (batch_size, target_sequence_length), optional) —
Indices of decoder input sequence tokens in the vocabulary.
Indices can be obtained using AutoTokenizer. See PreTrainedTokenizer.encode() and
PreTrainedTokenizer.call() for details.
What are decoder input IDs?
MT5 uses the pad_token_id as the starting token for decoder_input_ids generation. If past_key_values
is used, optionally only the last decoder_input_ids have to be input (see past_key_values).
To know more on how to prepare decoder_input_ids for pretraining take a look at MT5
Training.
decoder_attention_mask (torch.BoolTensor of shape (batch_size, target_sequence_length), optional) —
Default behavior: generate a tensor that ignores pad tokens in decoder_input_ids. Causal mask will also
be used by default.
head_mask (torch.FloatTensor of shape (num_heads,) or (num_layers, num_heads), optional) —
Mask to nullify selected heads of the self-attention modules in the encoder. Mask values selected in [0, 1]:
1 indicates the head is not masked,
0 indicates the head is masked.
decoder_head_mask (torch.FloatTensor of shape (num_heads,) or (num_layers, num_heads), optional) —
Mask to nullify selected heads of the self-attention modules in the decoder. Mask values selected in [0, 1]:
1 indicates the head is not masked,
0 indicates the head is masked.
cross_attn_head_mask (torch.Tensor of shape (num_heads,) or (num_layers, num_heads), optional) —
Mask to nullify selected heads of the cross-attention modules in the decoder. Mask values selected in
[0, 1]:
1 indicates the head is not masked,
0 indicates the head is masked.
encoder_outputs (tuple(tuple(torch.FloatTensor), optional) —
Tuple consists of (last_hidden_state, optional: hidden_states, optional: attentions)
last_hidden_state of shape (batch_size, sequence_length, hidden_size) is a sequence of hidden states at
the output of the last layer of the encoder. Used in the cross-attention of the decoder.
past_key_values (tuple(tuple(torch.FloatTensor)) of length config.n_layers with each tuple having 4 tensors of shape (batch_size, num_heads, sequence_length - 1, embed_size_per_head)) —
Contains precomputed key and value hidden states of the attention blocks. Can be used to speed up decoding.
If past_key_values are used, the user can optionally input only the last decoder_input_ids (those that
don’t have their past key value states given to this model) of shape (batch_size, 1) instead of all
decoder_input_ids of shape (batch_size, sequence_length).
inputs_embeds (torch.FloatTensor of shape (batch_size, sequence_length, hidden_size), optional) —
Optionally, instead of passing input_ids you can choose to directly pass an embedded representation. This
is useful if you want more control over how to convert input_ids indices into associated vectors than the
model’s internal embedding lookup matrix.
decoder_inputs_embeds (torch.FloatTensor of shape (batch_size, target_sequence_length, hidden_size), optional) —
Optionally, instead of passing decoder_input_ids you can choose to directly pass an embedded
representation. If past_key_values is used, optionally only the last decoder_inputs_embeds have to be
input (see past_key_values). This is useful if you want more control over how to convert
decoder_input_ids indices into associated vectors than the model’s internal embedding lookup matrix.
If decoder_input_ids and decoder_inputs_embeds are both unset, decoder_inputs_embeds takes the value
of inputs_embeds.
use_cache (bool, optional) —
If set to True, past_key_values key value states are returned and can be used to speed up decoding (see
past_key_values).
output_attentions (bool, optional) —
Whether or not to return the attentions tensors of all attention layers. See attentions under returned
tensors for more detail.
output_hidden_states (bool, optional) —
Whether or not to return the hidden states of all layers. See hidden_states under returned tensors for
more detail.
return_dict (bool, optional) —
Whether or not to return a ModelOutput instead of a plain tuple.
Returns
transformers.modeling_outputs.Seq2SeqModelOutput or tuple(torch.FloatTensor)
A transformers.modeling_outputs.Seq2SeqModelOutput or a tuple of
torch.FloatTensor (if return_dict=False is passed or when config.return_dict=False) comprising various
elements depending on the configuration (MT5Config) and inputs.
last_hidden_state (torch.FloatTensor of shape (batch_size, sequence_length, hidden_size)) — Sequence of hidden-states at the output of the last layer of the decoder of the model.
If past_key_values is used only the last hidden-state of the sequences of shape (batch_size, 1, hidden_size) is output.
past_key_values (tuple(tuple(torch.FloatTensor)), optional, returned when use_cache=True is passed or when config.use_cache=True) — Tuple of tuple(torch.FloatTensor) of length config.n_layers, with each tuple having 2 tensors of shape
(batch_size, num_heads, sequence_length, embed_size_per_head)) and 2 additional tensors of shape
(batch_size, num_heads, encoder_sequence_length, embed_size_per_head).
Contains pre-computed hidden-states (key and values in the self-attention blocks and in the cross-attention
blocks) that can be used (see past_key_values input) to speed up sequential decoding.
decoder_hidden_states (tuple(torch.FloatTensor), optional, returned when output_hidden_states=True is passed or when config.output_hidden_states=True) — Tuple of torch.FloatTensor (one for the output of the embeddings, if the model has an embedding layer, +
one for the output of each layer) of shape (batch_size, sequence_length, hidden_size).
Hidden-states of the decoder at the output of each layer plus the optional initial embedding outputs.
decoder_attentions (tuple(torch.FloatTensor), optional, returned when output_attentions=True is passed or when config.output_attentions=True) — Tuple of torch.FloatTensor (one for each layer) of shape (batch_size, num_heads, sequence_length, sequence_length).
Attentions weights of the decoder, after the attention softmax, used to compute the weighted average in the
self-attention heads.
cross_attentions (tuple(torch.FloatTensor), optional, returned when output_attentions=True is passed or when config.output_attentions=True) — Tuple of torch.FloatTensor (one for each layer) of shape (batch_size, num_heads, sequence_length, sequence_length).
Attentions weights of the decoder’s cross-attention layer, after the attention softmax, used to compute the
weighted average in the cross-attention heads.
encoder_last_hidden_state (torch.FloatTensor of shape (batch_size, sequence_length, hidden_size), optional) — Sequence of hidden-states at the output of the last layer of the encoder of the model.
encoder_hidden_states (tuple(torch.FloatTensor), optional, returned when output_hidden_states=True is passed or when config.output_hidden_states=True) — Tuple of torch.FloatTensor (one for the output of the embeddings, if the model has an embedding layer, +
one for the output of each layer) of shape (batch_size, sequence_length, hidden_size).
Hidden-states of the encoder at the output of each layer plus the optional initial embedding outputs.
encoder_attentions (tuple(torch.FloatTensor), optional, returned when output_attentions=True is passed or when config.output_attentions=True) — Tuple of torch.FloatTensor (one for each layer) of shape (batch_size, num_heads, sequence_length, sequence_length).
Attentions weights of the encoder, after the attention softmax, used to compute the weighted average in the
self-attention heads.
The MT5Model forward method, overrides the __call__ special method.
Although the recipe for forward pass needs to be defined within this function, one should call the Module
instance afterwards instead of this since the former takes care of running the pre and post processing steps while
the latter silently ignores them.
Example:
	Copied
 from transformers import AutoTokenizer, MT5Model
 tokenizer = AutoTokenizer.from_pretrained("mt5-small")
 model = MT5Model.from_pretrained("mt5-small")
 input_ids = tokenizer(
...     "Studies have been shown that owning a dog is good for you", return_tensors="pt"
... ).input_ids  # Batch size 1
 decoder_input_ids = tokenizer("Studies show that", return_tensors="pt").input_ids  # Batch size 1
 # preprocess: Prepend decoder_input_ids with start token which is pad token for MT5Model.
 # This is not needed for torch's MT5ForConditionalGeneration as it does this internally using labels arg.
 decoder_input_ids = model._shift_right(decoder_input_ids)
 # forward pass
 outputs = model(input_ids=input_ids, decoder_input_ids=decoder_input_ids)
 last_hidden_states = outputs.last_hidden_state
parallelize
<
source
>
(
device_map = None
)
Parameters 
device_map (Dict[int, list], optional, defaults to None) —
A dictionary that maps attention modules to devices. Note that the embedding module and LMHead are always
automatically mapped to the first device (for esoteric reasons). That means that the first device should
have fewer attention modules mapped to it than other devices. For reference, the mt5 models have the
following number of attention modules:
mt5-small: 6
mt5-base: 12
mt5-large: 24
mt5-xl: 24
mt5-xxl: 24
This is an experimental feature and is a subject to change at a moment’s notice.
Uses a device map to distribute attention modules of the model across several devices. If no device map is given,
it will evenly distribute blocks across all devices.
Example:
	Copied
# Here is an example of a device map on a machine with 4 GPUs using mt5-xl, which has a total of 24 attention modules:
model = MT5ForConditionalGeneration.from_pretrained("mt5-xl")
device_map = {
    0: [0, 1, 2],
    1: [3, 4, 5, 6, 7, 8, 9],
    2: [10, 11, 12, 13, 14, 15, 16],
    3: [17, 18, 19, 20, 21, 22, 23],
}
model.parallelize(device_map)
MT5ForConditionalGeneration
	
class transformers.MT5ForConditionalGeneration
<
source
>
(
config: MT5Config
)
Parameters 
config (MT5Config) — Model configuration class with all the parameters of the model.
Initializing with a config file does not load the weights associated with the model, only the
configuration. Check out the from_pretrained() method to load the model weights.
MT5 Model with a language modeling head on top.
The MT5 model was proposed in Exploring the Limits of Transfer Learning with a Unified Text-to-Text
Transformer by Colin Raffel, Noam Shazeer, Adam Roberts, Katherine Lee, Sharan
Narang, Michael Matena, Yanqi Zhou, Wei Li, Peter J. Liu. It’s an encoder decoder transformer pre-trained in a
text-to-text denoising generative setting.
This model inherits from PreTrainedModel. Check the superclass documentation for the generic methods the
library implements for all its model (such as downloading or saving, resizing the input embeddings, pruning heads
etc.)
This model is also a PyTorch torch.nn.Module subclass.
Use it as a regular PyTorch Module and refer to the PyTorch documentation for all matter related to general usage
and behavior.
Examples:
	Copied
 from transformers import MT5ForConditionalGeneration, AutoTokenizer
 model = MT5ForConditionalGeneration.from_pretrained("google/mt5-small")
 tokenizer = AutoTokenizer.from_pretrained("google/mt5-small")
 article = "UN Offizier sagt, dass weiter verhandelt werden muss in Syrien."
 summary = "Weiter Verhandlung in Syrien."
 inputs = tokenizer(article, text_target=summary, return_tensors="pt")
 outputs = model(**inputs)
 loss = outputs.loss
deparallelize
<
source
>
(
)
Moves the model to cpu from a model parallel state.
Example:
	Copied
# On a 4 GPU machine with mt5-xl:
model = MT5ForConditionalGeneration.from_pretrained("Mt5-xl")
device_map = {
    0: [0, 1, 2],
    1: [3, 4, 5, 6, 7, 8, 9],
    2: [10, 11, 12, 13, 14, 15, 16],
    3: [17, 18, 19, 20, 21, 22, 23],
}
model.parallelize(device_map)  # Splits the model across several devices
model.deparallelize()  # Put the model back on cpu and cleans memory by calling torch.cuda.empty_cache()
forward
<
source
>
(
input_ids: typing.Optional[torch.LongTensor] = None
attention_mask: typing.Optional[torch.FloatTensor] = None
decoder_input_ids: typing.Optional[torch.LongTensor] = None
decoder_attention_mask: typing.Optional[torch.BoolTensor] = None
head_mask: typing.Optional[torch.FloatTensor] = None
decoder_head_mask: typing.Optional[torch.FloatTensor] = None
cross_attn_head_mask: typing.Optional[torch.Tensor] = None
encoder_outputs: typing.Optional[typing.Tuple[typing.Tuple[torch.Tensor]]] = None
past_key_values: typing.Optional[typing.Tuple[typing.Tuple[torch.Tensor]]] = None
inputs_embeds: typing.Optional[torch.FloatTensor] = None
decoder_inputs_embeds: typing.Optional[torch.FloatTensor] = None
labels: typing.Optional[torch.LongTensor] = None
use_cache: typing.Optional[bool] = None
output_attentions: typing.Optional[bool] = None
output_hidden_states: typing.Optional[bool] = None
return_dict: typing.Optional[bool] = None
)
→
transformers.modeling_outputs.Seq2SeqLMOutput or tuple(torch.FloatTensor)
Parameters 
input_ids (torch.LongTensor of shape (batch_size, sequence_length)) —
Indices of input sequence tokens in the vocabulary. MT5 is a model with relative position embeddings so you
should be able to pad the inputs on both the right and the left.
Indices can be obtained using AutoTokenizer. See PreTrainedTokenizer.encode() and
PreTrainedTokenizer.call() for detail.
What are input IDs?
To know more on how to prepare input_ids for pretraining take a look a MT5 Training.
attention_mask (torch.FloatTensor of shape (batch_size, sequence_length), optional) —
Mask to avoid performing attention on padding token indices. Mask values selected in [0, 1]:
1 for tokens that are not masked,
0 for tokens that are masked.
What are attention masks?
decoder_input_ids (torch.LongTensor of shape (batch_size, target_sequence_length), optional) —
Indices of decoder input sequence tokens in the vocabulary.
Indices can be obtained using AutoTokenizer. See PreTrainedTokenizer.encode() and
PreTrainedTokenizer.call() for details.
What are decoder input IDs?
MT5 uses the pad_token_id as the starting token for decoder_input_ids generation. If past_key_values
is used, optionally only the last decoder_input_ids have to be input (see past_key_values).
To know more on how to prepare decoder_input_ids for pretraining take a look at MT5
Training.
decoder_attention_mask (torch.BoolTensor of shape (batch_size, target_sequence_length), optional) —
Default behavior: generate a tensor that ignores pad tokens in decoder_input_ids. Causal mask will also
be used by default.
head_mask (torch.FloatTensor of shape (num_heads,) or (num_layers, num_heads), optional) —
Mask to nullify selected heads of the self-attention modules in the encoder. Mask values selected in [0, 1]:
1 indicates the head is not masked,
0 indicates the head is masked.
decoder_head_mask (torch.FloatTensor of shape (num_heads,) or (num_layers, num_heads), optional) —
Mask to nullify selected heads of the self-attention modules in the decoder. Mask values selected in [0, 1]:
1 indicates the head is not masked,
0 indicates the head is masked.
cross_attn_head_mask (torch.Tensor of shape (num_heads,) or (num_layers, num_heads), optional) —
Mask to nullify selected heads of the cross-attention modules in the decoder. Mask values selected in
[0, 1]:
1 indicates the head is not masked,
0 indicates the head is masked.
encoder_outputs (tuple(tuple(torch.FloatTensor), optional) —
Tuple consists of (last_hidden_state, optional: hidden_states, optional: attentions)
last_hidden_state of shape (batch_size, sequence_length, hidden_size) is a sequence of hidden states at
the output of the last layer of the encoder. Used in the cross-attention of the decoder.
past_key_values (tuple(tuple(torch.FloatTensor)) of length config.n_layers with each tuple having 4 tensors of shape (batch_size, num_heads, sequence_length - 1, embed_size_per_head)) —
Contains precomputed key and value hidden states of the attention blocks. Can be used to speed up decoding.
If past_key_values are used, the user can optionally input only the last decoder_input_ids (those that
don’t have their past key value states given to this model) of shape (batch_size, 1) instead of all
decoder_input_ids of shape (batch_size, sequence_length).
inputs_embeds (torch.FloatTensor of shape (batch_size, sequence_length, hidden_size), optional) —
Optionally, instead of passing input_ids you can choose to directly pass an embedded representation. This
is useful if you want more control over how to convert input_ids indices into associated vectors than the
model’s internal embedding lookup matrix.
decoder_inputs_embeds (torch.FloatTensor of shape (batch_size, target_sequence_length, hidden_size), optional) —
Optionally, instead of passing decoder_input_ids you can choose to directly pass an embedded
representation. If past_key_values is used, optionally only the last decoder_inputs_embeds have to be
input (see past_key_values). This is useful if you want more control over how to convert
decoder_input_ids indices into associated vectors than the model’s internal embedding lookup matrix.
If decoder_input_ids and decoder_inputs_embeds are both unset, decoder_inputs_embeds takes the value
of inputs_embeds.
use_cache (bool, optional) —
If set to True, past_key_values key value states are returned and can be used to speed up decoding (see
past_key_values).
output_attentions (bool, optional) —
Whether or not to return the attentions tensors of all attention layers. See attentions under returned
tensors for more detail.
output_hidden_states (bool, optional) —
Whether or not to return the hidden states of all layers. See hidden_states under returned tensors for
more detail.
return_dict (bool, optional) —
Whether or not to return a ModelOutput instead of a plain tuple.
labels (torch.LongTensor of shape (batch_size,), optional) —
Labels for computing the sequence classification/regression loss. Indices should be in [-100, 0, ..., config.vocab_size - 1]. All labels set to -100 are ignored (masked), the loss is only computed for
labels in [0, ..., config.vocab_size]
Returns
transformers.modeling_outputs.Seq2SeqLMOutput or tuple(torch.FloatTensor)
A transformers.modeling_outputs.Seq2SeqLMOutput or a tuple of
torch.FloatTensor (if return_dict=False is passed or when config.return_dict=False) comprising various
elements depending on the configuration (MT5Config) and inputs.
loss (torch.FloatTensor of shape (1,), optional, returned when labels is provided) — Language modeling loss.
logits (torch.FloatTensor of shape (batch_size, sequence_length, config.vocab_size)) — Prediction scores of the language modeling head (scores for each vocabulary token before SoftMax).
past_key_values (tuple(tuple(torch.FloatTensor)), optional, returned when use_cache=True is passed or when config.use_cache=True) — Tuple of tuple(torch.FloatTensor) of length config.n_layers, with each tuple having 2 tensors of shape
(batch_size, num_heads, sequence_length, embed_size_per_head)) and 2 additional tensors of shape
(batch_size, num_heads, encoder_sequence_length, embed_size_per_head).
Contains pre-computed hidden-states (key and values in the self-attention blocks and in the cross-attention
blocks) that can be used (see past_key_values input) to speed up sequential decoding.
decoder_hidden_states (tuple(torch.FloatTensor), optional, returned when output_hidden_states=True is passed or when config.output_hidden_states=True) — Tuple of torch.FloatTensor (one for the output of the embeddings, if the model has an embedding layer, +
one for the output of each layer) of shape (batch_size, sequence_length, hidden_size).
Hidden-states of the decoder at the output of each layer plus the initial embedding outputs.
decoder_attentions (tuple(torch.FloatTensor), optional, returned when output_attentions=True is passed or when config.output_attentions=True) — Tuple of torch.FloatTensor (one for each layer) of shape (batch_size, num_heads, sequence_length, sequence_length).
Attentions weights of the decoder, after the attention softmax, used to compute the weighted average in the
self-attention heads.
cross_attentions (tuple(torch.FloatTensor), optional, returned when output_attentions=True is passed or when config.output_attentions=True) — Tuple of torch.FloatTensor (one for each layer) of shape (batch_size, num_heads, sequence_length, sequence_length).
Attentions weights of the decoder’s cross-attention layer, after the attention softmax, used to compute the
weighted average in the cross-attention heads.
encoder_last_hidden_state (torch.FloatTensor of shape (batch_size, sequence_length, hidden_size), optional) — Sequence of hidden-states at the output of the last layer of the encoder of the model.
encoder_hidden_states (tuple(torch.FloatTensor), optional, returned when output_hidden_states=True is passed or when config.output_hidden_states=True) — Tuple of torch.FloatTensor (one for the output of the embeddings, if the model has an embedding layer, +
one for the output of each layer) of shape (batch_size, sequence_length, hidden_size).
Hidden-states of the encoder at the output of each layer plus the initial embedding outputs.
encoder_attentions (tuple(torch.FloatTensor), optional, returned when output_attentions=True is passed or when config.output_attentions=True) — Tuple of torch.FloatTensor (one for each layer) of shape (batch_size, num_heads, sequence_length, sequence_length).
Attentions weights of the encoder, after the attention softmax, used to compute the weighted average in the
self-attention heads.
The MT5ForConditionalGeneration forward method, overrides the __call__ special method.
Although the recipe for forward pass needs to be defined within this function, one should call the Module
instance afterwards instead of this since the former takes care of running the pre and post processing steps while
the latter silently ignores them.
Examples:
	Copied
 from transformers import AutoTokenizer, MT5ForConditionalGeneration
 tokenizer = AutoTokenizer.from_pretrained("mt5-small")
 model = MT5ForConditionalGeneration.from_pretrained("mt5-small")
 # training
 input_ids = tokenizer("The <extra_id_0> walks in <extra_id_1> park", return_tensors="pt").input_ids
 labels = tokenizer("<extra_id_0> cute dog <extra_id_1> the <extra_id_2>", return_tensors="pt").input_ids
 outputs = model(input_ids=input_ids, labels=labels)
 loss = outputs.loss
 logits = outputs.logits
 # inference
 input_ids = tokenizer(
...     "summarize: studies have shown that owning a dog is good for you", return_tensors="pt"
... ).input_ids  # Batch size 1
 outputs = model.generate(input_ids)
 print(tokenizer.decode(outputs[0], skip_special_tokens=True))
 # studies have shown that owning a dog is good for you.
parallelize
<
source
>
(
device_map = None
)
Parameters 
device_map (Dict[int, list], optional, defaults to None) —
A dictionary that maps attention modules to devices. Note that the embedding module and LMHead are always
automatically mapped to the first device (for esoteric reasons). That means that the first device should
have fewer attention modules mapped to it than other devices. For reference, the mt5 models have the
following number of attention modules:
mt5-small: 6
mt5-base: 12
mt5-large: 24
mt5-xl: 24
mt5-xxl: 24
This is an experimental feature and is a subject to change at a moment’s notice.
Uses a device map to distribute attention modules of the model across several devices. If no device map is given,
it will evenly distribute blocks across all devices.
Example:
	Copied
# Here is an example of a device map on a machine with 4 GPUs using mt5-xl, which has a total of 24 attention modules:
model = MT5ForConditionalGeneration.from_pretrained("mt5-xl")
device_map = {
    0: [0, 1, 2],
    1: [3, 4, 5, 6, 7, 8, 9],
    2: [10, 11, 12, 13, 14, 15, 16],
    3: [17, 18, 19, 20, 21, 22, 23],
}
model.parallelize(device_map)
MT5EncoderModel
	
class transformers.MT5EncoderModel
<
source
>
(
config: MT5Config
)
Parameters 
config (MT5Config) — Model configuration class with all the parameters of the model.
Initializing with a config file does not load the weights associated with the model, only the
configuration. Check out the from_pretrained() method to load the model weights.
The bare MT5 Model transformer outputting encoder’s raw hidden-states without any specific head on top.
The MT5 model was proposed in Exploring the Limits of Transfer Learning with a Unified Text-to-Text
Transformer by Colin Raffel, Noam Shazeer, Adam Roberts, Katherine Lee, Sharan
Narang, Michael Matena, Yanqi Zhou, Wei Li, Peter J. Liu. It’s an encoder decoder transformer pre-trained in a
text-to-text denoising generative setting.
This model inherits from PreTrainedModel. Check the superclass documentation for the generic methods the
library implements for all its model (such as downloading or saving, resizing the input embeddings, pruning heads
etc.)
This model is also a PyTorch torch.nn.Module subclass.
Use it as a regular PyTorch Module and refer to the PyTorch documentation for all matter related to general usage
and behavior.
Examples:
	Copied
 from transformers import MT5EncoderModel, AutoTokenizer
 model = MT5EncoderModel.from_pretrained("google/mt5-small")
 tokenizer = AutoTokenizer.from_pretrained("google/mt5-small")
 article = "UN Offizier sagt, dass weiter verhandelt werden muss in Syrien."
 input_ids = tokenizer(article, return_tensors="pt").input_ids
 outputs = model(input_ids)
 hidden_state = outputs.last_hidden_state
deparallelize
<
source
>
(
)
Moves the model to cpu from a model parallel state.
Example:
	Copied
# On a 4 GPU machine with mt5-xl:
model = MT5ForConditionalGeneration.from_pretrained("Mt5-xl")
device_map = {
    0: [0, 1, 2],
    1: [3, 4, 5, 6, 7, 8, 9],
    2: [10, 11, 12, 13, 14, 15, 16],
    3: [17, 18, 19, 20, 21, 22, 23],
}
model.parallelize(device_map)  # Splits the model across several devices
model.deparallelize()  # Put the model back on cpu and cleans memory by calling torch.cuda.empty_cache()
forward
<
source
>
(
input_ids: typing.Optional[torch.LongTensor] = None
attention_mask: typing.Optional[torch.FloatTensor] = None
head_mask: typing.Optional[torch.FloatTensor] = None
inputs_embeds: typing.Optional[torch.FloatTensor] = None
output_attentions: typing.Optional[bool] = None
output_hidden_states: typing.Optional[bool] = None
return_dict: typing.Optional[bool] = None
)
→
transformers.modeling_outputs.BaseModelOutput or tuple(torch.FloatTensor)
Parameters 
input_ids (torch.LongTensor of shape (batch_size, sequence_length)) —
Indices of input sequence tokens in the vocabulary. MT5 is a model with relative position embeddings so you
should be able to pad the inputs on both the right and the left.
Indices can be obtained using AutoTokenizer. See PreTrainedTokenizer.encode() and
PreTrainedTokenizer.call() for detail.
To know more on how to prepare input_ids for pretraining take a look a MT5 Training.
attention_mask (torch.FloatTensor of shape (batch_size, sequence_length), optional) —
Mask to avoid performing attention on padding token indices. Mask values selected in [0, 1]:
1 for tokens that are not masked,
0 for tokens that are masked.
What are attention masks?
head_mask (torch.FloatTensor of shape (num_heads,) or (num_layers, num_heads), optional) —
Mask to nullify selected heads of the self-attention modules. Mask values selected in [0, 1]:
1 indicates the head is not masked,
0 indicates the head is masked.
inputs_embeds (torch.FloatTensor of shape (batch_size, sequence_length, hidden_size), optional) —
Optionally, instead of passing input_ids you can choose to directly pass an embedded representation. This
is useful if you want more control over how to convert input_ids indices into associated vectors than the
model’s internal embedding lookup matrix.
output_attentions (bool, optional) —
Whether or not to return the attentions tensors of all attention layers. See attentions under returned
tensors for more detail.
output_hidden_states (bool, optional) —
Whether or not to return the hidden states of all layers. See hidden_states under returned tensors for
more detail.
return_dict (bool, optional) —
Whether or not to return a ModelOutput instead of a plain tuple.
Returns
transformers.modeling_outputs.BaseModelOutput or tuple(torch.FloatTensor)
A transformers.modeling_outputs.BaseModelOutput or a tuple of
torch.FloatTensor (if return_dict=False is passed or when config.return_dict=False) comprising various
elements depending on the configuration (MT5Config) and inputs.
last_hidden_state (torch.FloatTensor of shape (batch_size, sequence_length, hidden_size)) — Sequence of hidden-states at the output of the last layer of the model.
hidden_states (tuple(torch.FloatTensor), optional, returned when output_hidden_states=True is passed or when config.output_hidden_states=True) — Tuple of torch.FloatTensor (one for the output of the embeddings, if the model has an embedding layer, +
one for the output of each layer) of shape (batch_size, sequence_length, hidden_size).
Hidden-states of the model at the output of each layer plus the optional initial embedding outputs.
attentions (tuple(torch.FloatTensor), optional, returned when output_attentions=True is passed or when config.output_attentions=True) — Tuple of torch.FloatTensor (one for each layer) of shape (batch_size, num_heads, sequence_length, sequence_length).
Attentions weights after the attention softmax, used to compute the weighted average in the self-attention
heads.
The MT5EncoderModel forward method, overrides the __call__ special method.
Although the recipe for forward pass needs to be defined within this function, one should call the Module
instance afterwards instead of this since the former takes care of running the pre and post processing steps while
the latter silently ignores them.
Example:
	Copied
 from transformers import AutoTokenizer, MT5EncoderModel
 tokenizer = AutoTokenizer.from_pretrained("mt5-small")
 model = MT5EncoderModel.from_pretrained("mt5-small")
 input_ids = tokenizer(
...     "Studies have been shown that owning a dog is good for you", return_tensors="pt"
... ).input_ids  # Batch size 1
 outputs = model(input_ids=input_ids)
 last_hidden_states = outputs.last_hidden_state
parallelize
<
source
>
(
device_map = None
)
Parameters 
device_map (Dict[int, list], optional, defaults to None) —
A dictionary that maps attention modules to devices. Note that the embedding module and LMHead are always
automatically mapped to the first device (for esoteric reasons). That means that the first device should
have fewer attention modules mapped to it than other devices. For reference, the mt5 models have the
following number of attention modules:
mt5-small: 6
mt5-base: 12
mt5-large: 24
mt5-xl: 24
mt5-xxl: 24
This is an experimental feature and is a subject to change at a moment’s notice.
Uses a device map to distribute attention modules of the model across several devices. If no device map is given,
it will evenly distribute blocks across all devices.
Example:
	Copied
# Here is an example of a device map on a machine with 4 GPUs using mt5-xl, which has a total of 24 attention modules:
model = MT5ForConditionalGeneration.from_pretrained("mt5-xl")
device_map = {
    0: [0, 1, 2],
    1: [3, 4, 5, 6, 7, 8, 9],
    2: [10, 11, 12, 13, 14, 15, 16],
    3: [17, 18, 19, 20, 21, 22, 23],
}
model.parallelize(device_map)
MT5ForQuestionAnswering
	
class transformers.MT5ForQuestionAnswering
<
source
>
(
config: MT5Config
)
Parameters 
config (MT5Config) — Model configuration class with all the parameters of the model.
Initializing with a config file does not load the weights associated with the model, only the
configuration. Check out the from_pretrained() method to load the model weights.
MT5 Model with a span classification head on top for extractive question-answering tasks like SQuAD (linear layers
on top of the hidden-states output to compute span start logits and span end logits).
The MT5 model was proposed in Exploring the Limits of Transfer Learning with a Unified Text-to-Text
Transformer by Colin Raffel, Noam Shazeer, Adam Roberts, Katherine Lee, Sharan
Narang, Michael Matena, Yanqi Zhou, Wei Li, Peter J. Liu. It’s an encoder decoder transformer pre-trained in a
text-to-text denoising generative setting.
This model inherits from PreTrainedModel. Check the superclass documentation for the generic methods the
library implements for all its model (such as downloading or saving, resizing the input embeddings, pruning heads
etc.)
This model is also a PyTorch torch.nn.Module subclass.
Use it as a regular PyTorch Module and refer to the PyTorch documentation for all matter related to general usage
and behavior.
forward
<
source
>
(
input_ids: typing.Optional[torch.LongTensor] = None
attention_mask: typing.Optional[torch.FloatTensor] = None
decoder_input_ids: typing.Optional[torch.LongTensor] = None
decoder_attention_mask: typing.Optional[torch.BoolTensor] = None
head_mask: typing.Optional[torch.FloatTensor] = None
decoder_head_mask: typing.Optional[torch.FloatTensor] = None
cross_attn_head_mask: typing.Optional[torch.Tensor] = None
encoder_outputs: typing.Optional[typing.Tuple[typing.Tuple[torch.Tensor]]] = None
start_positions: typing.Optional[torch.LongTensor] = None
end_positions: typing.Optional[torch.LongTensor] = None
inputs_embeds: typing.Optional[torch.FloatTensor] = None
decoder_inputs_embeds: typing.Optional[torch.FloatTensor] = None
use_cache: typing.Optional[bool] = None
output_attentions: typing.Optional[bool] = None
output_hidden_states: typing.Optional[bool] = None
return_dict: typing.Optional[bool] = None
)
→
transformers.modeling_outputs.Seq2SeqQuestionAnsweringModelOutput or tuple(torch.FloatTensor)
Parameters 
input_ids (torch.LongTensor of shape (batch_size, sequence_length)) —
Indices of input sequence tokens in the vocabulary. MT5 is a model with relative position embeddings so you
should be able to pad the inputs on both the right and the left.
Indices can be obtained using AutoTokenizer. See PreTrainedTokenizer.encode() and
PreTrainedTokenizer.call() for detail.
What are input IDs?
To know more on how to prepare input_ids for pretraining take a look a MT5 Training.
attention_mask (torch.FloatTensor of shape (batch_size, sequence_length), optional) —
Mask to avoid performing attention on padding token indices. Mask values selected in [0, 1]:
1 for tokens that are not masked,
0 for tokens that are masked.
What are attention masks?
decoder_input_ids (torch.LongTensor of shape (batch_size, target_sequence_length), optional) —
Indices of decoder input sequence tokens in the vocabulary.
Indices can be obtained using AutoTokenizer. See PreTrainedTokenizer.encode() and
PreTrainedTokenizer.call() for details.
What are decoder input IDs?
MT5 uses the pad_token_id as the starting token for decoder_input_ids generation. If past_key_values
is used, optionally only the last decoder_input_ids have to be input (see past_key_values).
To know more on how to prepare decoder_input_ids for pretraining take a look at MT5
Training.
decoder_attention_mask (torch.BoolTensor of shape (batch_size, target_sequence_length), optional) —
Default behavior: generate a tensor that ignores pad tokens in decoder_input_ids. Causal mask will also
be used by default.
head_mask (torch.FloatTensor of shape (num_heads,) or (num_layers, num_heads), optional) —
Mask to nullify selected heads of the self-attention modules in the encoder. Mask values selected in [0, 1]:
1 indicates the head is not masked,
0 indicates the head is masked.
decoder_head_mask (torch.FloatTensor of shape (num_heads,) or (num_layers, num_heads), optional) —
Mask to nullify selected heads of the self-attention modules in the decoder. Mask values selected in [0, 1]:
1 indicates the head is not masked,
0 indicates the head is masked.
cross_attn_head_mask (torch.Tensor of shape (num_heads,) or (num_layers, num_heads), optional) —
Mask to nullify selected heads of the cross-attention modules in the decoder. Mask values selected in
[0, 1]:
1 indicates the head is not masked,
0 indicates the head is masked.
encoder_outputs (tuple(tuple(torch.FloatTensor), optional) —
Tuple consists of (last_hidden_state, optional: hidden_states, optional: attentions)
last_hidden_state of shape (batch_size, sequence_length, hidden_size) is a sequence of hidden states at
the output of the last layer of the encoder. Used in the cross-attention of the decoder.
past_key_values (tuple(tuple(torch.FloatTensor)) of length config.n_layers with each tuple having 4 tensors of shape (batch_size, num_heads, sequence_length - 1, embed_size_per_head)) —
Contains precomputed key and value hidden states of the attention blocks. Can be used to speed up decoding.
If past_key_values are used, the user can optionally input only the last decoder_input_ids (those that
don’t have their past key value states given to this model) of shape (batch_size, 1) instead of all
decoder_input_ids of shape (batch_size, sequence_length).
inputs_embeds (torch.FloatTensor of shape (batch_size, sequence_length, hidden_size), optional) —
Optionally, instead of passing input_ids you can choose to directly pass an embedded representation. This
is useful if you want more control over how to convert input_ids indices into associated vectors than the
model’s internal embedding lookup matrix.
decoder_inputs_embeds (torch.FloatTensor of shape (batch_size, target_sequence_length, hidden_size), optional) —
Optionally, instead of passing decoder_input_ids you can choose to directly pass an embedded
representation. If past_key_values is used, optionally only the last decoder_inputs_embeds have to be
input (see past_key_values). This is useful if you want more control over how to convert
decoder_input_ids indices into associated vectors than the model’s internal embedding lookup matrix.
If decoder_input_ids and decoder_inputs_embeds are both unset, decoder_inputs_embeds takes the value
of inputs_embeds.
use_cache (bool, optional) —
If set to True, past_key_values key value states are returned and can be used to speed up decoding (see
past_key_values).
output_attentions (bool, optional) —
Whether or not to return the attentions tensors of all attention layers. See attentions under returned
tensors for more detail.
output_hidden_states (bool, optional) —
Whether or not to return the hidden states of all layers. See hidden_states under returned tensors for
more detail.
return_dict (bool, optional) —
Whether or not to return a ModelOutput instead of a plain tuple.
start_positions (torch.LongTensor of shape (batch_size,), optional) —
Labels for position (index) of the start of the labelled span for computing the token classification loss.
Positions are clamped to the length of the sequence (sequence_length). Position outside of the sequence
are not taken into account for computing the loss.
end_positions (torch.LongTensor of shape (batch_size,), optional) —
Labels for position (index) of the end of the labelled span for computing the token classification loss.
Positions are clamped to the length of the sequence (sequence_length). Position outside of the sequence
are not taken into account for computing the loss.
Returns
transformers.modeling_outputs.Seq2SeqQuestionAnsweringModelOutput or tuple(torch.FloatTensor)
A transformers.modeling_outputs.Seq2SeqQuestionAnsweringModelOutput or a tuple of
torch.FloatTensor (if return_dict=False is passed or when config.return_dict=False) comprising various
elements depending on the configuration (MT5Config) and inputs.
loss (torch.FloatTensor of shape (1,), optional, returned when labels is provided) — Total span extraction loss is the sum of a Cross-Entropy for the start and end positions.
start_logits (torch.FloatTensor of shape (batch_size, sequence_length)) — Span-start scores (before SoftMax).
end_logits (torch.FloatTensor of shape (batch_size, sequence_length)) — Span-end scores (before SoftMax).
past_key_values (tuple(tuple(torch.FloatTensor)), optional, returned when use_cache=True is passed or when config.use_cache=True) — Tuple of tuple(torch.FloatTensor) of length config.n_layers, with each tuple having 2 tensors of shape
(batch_size, num_heads, sequence_length, embed_size_per_head)) and 2 additional tensors of shape
(batch_size, num_heads, encoder_sequence_length, embed_size_per_head).
Contains pre-computed hidden-states (key and values in the self-attention blocks and in the cross-attention
blocks) that can be used (see past_key_values input) to speed up sequential decoding.
decoder_hidden_states (tuple(torch.FloatTensor), optional, returned when output_hidden_states=True is passed or when config.output_hidden_states=True) — Tuple of torch.FloatTensor (one for the output of the embeddings, if the model has an embedding layer, +
one for the output of each layer) of shape (batch_size, sequence_length, hidden_size).
Hidden-states of the decoder at the output of each layer plus the initial embedding outputs.
decoder_attentions (tuple(torch.FloatTensor), optional, returned when output_attentions=True is passed or when config.output_attentions=True) — Tuple of torch.FloatTensor (one for each layer) of shape (batch_size, num_heads, sequence_length, sequence_length).
Attentions weights of the decoder, after the attention softmax, used to compute the weighted average in the
self-attention heads.
cross_attentions (tuple(torch.FloatTensor), optional, returned when output_attentions=True is passed or when config.output_attentions=True) — Tuple of torch.FloatTensor (one for each layer) of shape (batch_size, num_heads, sequence_length, sequence_length).
Attentions weights of the decoder’s cross-attention layer, after the attention softmax, used to compute the
weighted average in the cross-attention heads.
encoder_last_hidden_state (torch.FloatTensor of shape (batch_size, sequence_length, hidden_size), optional) — Sequence of hidden-states at the output of the last layer of the encoder of the model.
encoder_hidden_states (tuple(torch.FloatTensor), optional, returned when output_hidden_states=True is passed or when config.output_hidden_states=True) — Tuple of torch.FloatTensor (one for the output of the embeddings, if the model has an embedding layer, +
one for the output of each layer) of shape (batch_size, sequence_length, hidden_size).
Hidden-states of the encoder at the output of each layer plus the initial embedding outputs.
encoder_attentions (tuple(torch.FloatTensor), optional, returned when output_attentions=True is passed or when config.output_attentions=True) — Tuple of torch.FloatTensor (one for each layer) of shape (batch_size, num_heads, sequence_length, sequence_length).
Attentions weights of the encoder, after the attention softmax, used to compute the weighted average in the
self-attention heads.
The MT5ForQuestionAnswering forward method, overrides the __call__ special method.
Although the recipe for forward pass needs to be defined within this function, one should call the Module
instance afterwards instead of this since the former takes care of running the pre and post processing steps while
the latter silently ignores them.
TFMT5Model
	
class transformers.TFMT5Model
<
source
>
(
*args
**kwargs
)
This class overrides TFT5Model. Please check the superclass for the appropriate documentation alongside usage
examples.
Examples:
	Copied
 from transformers import TFMT5Model, AutoTokenizer
 model = TFMT5Model.from_pretrained("google/mt5-small")
 tokenizer = AutoTokenizer.from_pretrained("google/mt5-small")
 article = "UN Offizier sagt, dass weiter verhandelt werden muss in Syrien."
 summary = "Weiter Verhandlung in Syrien."
 inputs = tokenizer(article, return_tensors="tf")
 labels = tokenizer(text_target=summary, return_tensors="tf")
 outputs = model(input_ids=inputs["input_ids"], decoder_input_ids=labels["input_ids"])
 hidden_states = outputs.last_hidden_state
TFMT5ForConditionalGeneration
	
class transformers.TFMT5ForConditionalGeneration
<
source
>
(
*args
**kwargs
)
This class overrides TFT5ForConditionalGeneration. Please check the superclass for the appropriate
documentation alongside usage examples.
Examples:
	Copied
 from transformers import TFMT5ForConditionalGeneration, AutoTokenizer
 model = TFMT5ForConditionalGeneration.from_pretrained("google/mt5-small")
 tokenizer = AutoTokenizer.from_pretrained("google/mt5-small")
 article = "UN Offizier sagt, dass weiter verhandelt werden muss in Syrien."
 summary = "Weiter Verhandlung in Syrien."
 inputs = tokenizer(article, text_target=summary, return_tensors="tf")
 outputs = model(**inputs)
 loss = outputs.loss
TFMT5EncoderModel
	
class transformers.TFMT5EncoderModel
<
source
>
(
*args
**kwargs
)
This class overrides TFT5EncoderModel. Please check the superclass for the appropriate documentation alongside
usage examples.
Examples:
	Copied
 from transformers import TFMT5EncoderModel, AutoTokenizer
 model = TFMT5EncoderModel.from_pretrained("google/mt5-small")
 tokenizer = AutoTokenizer.from_pretrained("google/mt5-small")
 article = "UN Offizier sagt, dass weiter verhandelt werden muss in Syrien."
 input_ids = tokenizer(article, return_tensors="tf").input_ids
 outputs = model(input_ids)
 hidden_state = outputs.last_hidden_state
FlaxMT5Model
	
class transformers.FlaxMT5Model
<
source
>
(
config: T5Config
input_shape: typing.Tuple[int] = (1, 1)
seed: int = 0
dtype: dtype = <class 'jax.numpy.float32'>
_do_init: bool = True
gradient_checkpointing: bool = False
**kwargs
)
This class overrides FlaxT5Model. Please check the superclass for the appropriate documentation alongside usage
examples.
Examples:
	Copied
 from transformers import FlaxMT5Model, AutoTokenizer
 model = FlaxMT5Model.from_pretrained("google/mt5-small")
 tokenizer = AutoTokenizer.from_pretrained("google/mt5-small")
 article = "UN Offizier sagt, dass weiter verhandelt werden muss in Syrien."
 summary = "Weiter Verhandlung in Syrien."
 inputs = tokenizer(article, return_tensors="np")
 decoder_input_ids = tokenizer(text_target=summary, return_tensors="np").input_ids
 outputs = model(input_ids=inputs["input_ids"], decoder_input_ids=decoder_input_ids)
 hidden_states = outputs.last_hidden_state
FlaxMT5ForConditionalGeneration
	
class transformers.FlaxMT5ForConditionalGeneration
<
source
>
(
config: T5Config
input_shape: typing.Tuple[int] = (1, 1)
seed: int = 0
dtype: dtype = <class 'jax.numpy.float32'>
_do_init: bool = True
gradient_checkpointing: bool = False
**kwargs
)
This class overrides FlaxT5ForConditionalGeneration. Please check the superclass for the appropriate
documentation alongside usage examples.
Examples:
	Copied
 from transformers import FlaxMT5ForConditionalGeneration, AutoTokenizer
 model = FlaxMT5ForConditionalGeneration.from_pretrained("google/mt5-small")
 tokenizer = AutoTokenizer.from_pretrained("google/mt5-small")
 article = "UN Offizier sagt, dass weiter verhandelt werden muss in Syrien."
 summary = "Weiter Verhandlung in Syrien."
 inputs = tokenizer(article, return_tensors="np")
 decoder_input_ids = tokenizer(text_target=summary, return_tensors="np").input_ids
 outputs = model(**inputs, decoder_input_ids=decoder_input_ids)
 logits = outputs.logits
FlaxMT5EncoderModel
	
class transformers.FlaxMT5EncoderModel
<
source
>
(
config: T5Config
input_shape: typing.Tuple[int] = (1, 1)
seed: int = 0
dtype: dtype = <class 'jax.numpy.float32'>
_do_init: bool = True
gradient_checkpointing: bool = False
**kwargs
)
This class overrides FlaxT5EncoderModel. Please check the superclass for the appropriate documentation
alongside usage examples.
Examples:
	Copied
 from transformers import FlaxT5EncoderModel, AutoTokenizer
 model = FlaxT5EncoderModel.from_pretrained("google/mt5-small")
 tokenizer = AutoTokenizer.from_pretrained("google/mt5-small")
 article = "UN Offizier sagt, dass weiter verhandelt werden muss in Syrien."
 summary = "Weiter Verhandlung in Syrien."
 inputs = tokenizer(article, return_tensors="np")
 decoder_input_ids = tokenizer(text_target=summary, return_tensors="np").input_ids
 outputs = model(input_ids=inputs["input_ids"])
 hidden_states = outputs.last_hidden_state
←MRA
MVP→
mT5
Overview
Documentation resources
MT5Config
MT5Tokenizer
MT5TokenizerFast
MT5Model
MT5ForConditionalGeneration
MT5EncoderModel
MT5ForQuestionAnswering
TFMT5Model
TFMT5ForConditionalGeneration
TFMT5EncoderModel
FlaxMT5Model
FlaxMT5ForConditionalGeneration
FlaxMT5EncoderModel
