invalid data type 'str' at _convert_outputs in arrow_dataset.py
I think you're having this issue because you try to format strings as pytorch tensors, which is not possible.
Indeed by having "Text" in `columns=['Text','Label']`, you try to convert the text values to pytorch tensors.

Instead I recommend you to first tokenize your dataset using a tokenizer from transformers. For example

```python
from transformers import BertTokenizer
tokenizer = BertTokenizer.from_pretrained("bert-base-uncased")

train_dataset.map(lambda x: tokenizer(x["Text"]), batched=True)
train_dataset.set_format("torch", column=["input_ids"])
```

Another way to fix your issue would be to not set the format to pytorch, and leave the dataset as it is by default. In that case, the strings are returned normally when you get examples from your dataloader. It means that you would have to tokenize the examples in the training loop (or using a data collator) though.

Let me know if you have other questions
I trying to build multi label text classifier model using Transformers lib. 

I'm using Transformers NLP to load the data set, while calling trainer.train() method. It throws the following error 

File "C:\***\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'

I'm using pyarrow 1.0.0.  And I have simple custom data set with Text and Integer Label.  
Ex: Data
 Text ,     Label  #Column Header
 I'm facing an Network issue, 1
 I forgot my password, 2

Error StackTrace:

File "C:\**\transformers\trainer.py", line 492, in train
    for step, inputs in enumerate(epoch_iterator):
  File "C:\**\tqdm\std.py", line 1104, in __iter__
    for obj in iterable:
  File "C:\**\torch\utils\data\dataloader.py", line 345, in __next__
    data = self._next_data()
  File "C:\**\torch\utils\data\dataloader.py", line 385, in _next_data
    data = self._dataset_fetcher.fetch(index)  # may raise StopIteration
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in fetch
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in <listcomp>
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\nlp\arrow_dataset.py", line 414, in __getitem__
    output_all_columns=self._output_all_columns,
  File "C:\**\nlp\arrow_dataset.py", line 403, in _getitem
    outputs, format_type=format_type, format_columns=format_columns, output_all_columns=output_all_columns
  File "C:\**\nlp\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'
 

invalid data type 'str' at _convert_outputs in arrow_dataset.py 
 I trying to build multi label text classifier model using Transformers lib. 

I'm using Transformers NLP to load the data set, while calling trainer.train() method. It throws the following error 

File "C:\***\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'

I'm using pyarrow 1.0.0.  And I have simple custom data set with Text and Integer Label.  
Ex: Data
 Text ,     Label  #Column Header
 I'm facing an Network issue, 1
 I forgot my password, 2

Error StackTrace:

File "C:\**\transformers\trainer.py", line 492, in train
    for step, inputs in enumerate(epoch_iterator):
  File "C:\**\tqdm\std.py", line 1104, in __iter__
    for obj in iterable:
  File "C:\**\torch\utils\data\dataloader.py", line 345, in __next__
    data = self._next_data()
  File "C:\**\torch\utils\data\dataloader.py", line 385, in _next_data
    data = self._dataset_fetcher.fetch(index)  # may raise StopIteration
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in fetch
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\torch\utils\data\_utils\fetch.py", line 44, in <listcomp>
    data = [self.dataset[idx] for idx in possibly_batched_index]
  File "C:\**\nlp\arrow_dataset.py", line 414, in __getitem__
    output_all_columns=self._output_all_columns,
  File "C:\**\nlp\arrow_dataset.py", line 403, in _getitem
    outputs, format_type=format_type, format_columns=format_columns, output_all_columns=output_all_columns
  File "C:\**\nlp\arrow_dataset.py", line 343, in _convert_outputs
    v = command(v)
TypeError: new(): invalid data type 'str'
 
 
 I think you're having this issue because you try to format strings as pytorch tensors, which is not possible.
Indeed by having "Text" in `columns=['Text','Label']`, you try to convert the text values to pytorch tensors.

Instead I recommend you to first tokenize your dataset using a tokenizer from transformers. For example

```python
from transformers import BertTokenizer
tokenizer = BertTokenizer.from_pretrained("bert-base-uncased")

train_dataset.map(lambda x: tokenizer(x["Text"]), batched=True)
train_dataset.set_format("torch", column=["input_ids"])
```

Another way to fix your issue would be to not set the format to pytorch, and leave the dataset as it is by default. In that case, the strings are returned normally when you get examples from your dataloader. It means that you would have to tokenize the examples in the training loop (or using a data collator) though.

Let me know if you have other questions