KeyError: 'validation' when trying to use validation dataset

Hello,

When loading my dataset using the following code:

dataset = load_dataset('csv', data_files={'train': ['/content/drive/data.csv'],
                                              'validation': '/content/drive/data.csv'})

I try to execute the following code:

trainer = Trainer(
    model=model,
    args=training_args,
    train_dataset=lm_datasets["train"],
    eval_dataset=lm_datasets["validation"],
    data_collator=data_collator,
)

But then I get this error for some reason, which makes no sense:

---------------------------------------------------------------------------

KeyError                                  Traceback (most recent call last)

<ipython-input-35-a5580f1a4d07> in <module>()
      3     args=training_args,
      4     train_dataset=lm_datasets["train"],
----> 5     eval_dataset=lm_datasets["validation"],
      6     data_collator=data_collator,
      7 )

/usr/local/lib/python3.7/dist-packages/datasets/dataset_dict.py in __getitem__(self, k)
     35     def __getitem__(self, k) -> Dataset:
     36         if isinstance(k, (str, NamedSplit)) or len(self) == 0:
---> 37             return super().__getitem__(k)
     38         else:
     39             available_suggested_splits = [

KeyError: 'validation'