Is dataset iterative or not?
Hi there, 
Here is what I am trying, this is not working for me in map-style datasets, could you please tell me how to use datasets with being able to access ___getitem__ ? could you assist me please correcting this example? I need map-style datasets which is formed from concatenation of two datasets from your library. thanks 


```
import datasets
dataset1 = load_dataset("squad", split="train[:10]")
dataset1 = dataset1.map(lambda example: {"src_texts": "question: {0} context: {1} ".format(
    example["question"], example["context"]),
    "tgt_texts": example["answers"]["text"][0]}, remove_columns=dataset1.column_names)
dataset2 = load_dataset("imdb", split="train[:10]")
dataset2 = dataset2.map(lambda example: {"src_texts": "imdb: " + example["text"],
            "tgt_texts": str(example["label"])}, remove_columns=dataset2.column_names)
train_dataset = datasets.concatenate_datasets([dataset1, dataset2])
train_dataset.set_format(type='torch', columns=['src_texts', 'tgt_texts'])
dataloader = torch.utils.data.DataLoader(train_dataset, batch_size=32)
for id, batch in enumerate(dataloader):
    print(batch)

```
Hi
I want to use your library for large-scale training, I am not sure if this is implemented as iterative datasets or not?
could you provide me with example how I can use datasets as iterative datasets?
thanks
Is dataset iterative or not? 
 Hi
I want to use your library for large-scale training, I am not sure if this is implemented as iterative datasets or not?
could you provide me with example how I can use datasets as iterative datasets?
thanks 
 Hi there, 
Here is what I am trying, this is not working for me in map-style datasets, could you please tell me how to use datasets with being able to access ___getitem__ ? could you assist me please correcting this example? I need map-style datasets which is formed from concatenation of two datasets from your library. thanks 


```
import datasets
dataset1 = load_dataset("squad", split="train[:10]")
dataset1 = dataset1.map(lambda example: {"src_texts": "question: {0} context: {1} ".format(
    example["question"], example["context"]),
    "tgt_texts": example["answers"]["text"][0]}, remove_columns=dataset1.column_names)
dataset2 = load_dataset("imdb", split="train[:10]")
dataset2 = dataset2.map(lambda example: {"src_texts": "imdb: " + example["text"],
            "tgt_texts": str(example["label"])}, remove_columns=dataset2.column_names)
train_dataset = datasets.concatenate_datasets([dataset1, dataset2])
train_dataset.set_format(type='torch', columns=['src_texts', 'tgt_texts'])
dataloader = torch.utils.data.DataLoader(train_dataset, batch_size=32)
for id, batch in enumerate(dataloader):
    print(batch)

```