load_dataset for CSV files not working
In this case the user expects to get only one dataset object instead of the dictionary of datasets since only one csv file was specified without any split specifications.
I'm ok with returning the dataset object if no split specifications are given for text/json/csv/pandas.

For the other datasets ton the other hand the user doesn't know in advance the splits so I would keep the dictionary by default. What do you think ?
Similar to #622, I've noticed there is a problem when trying to load a CSV file with datasets.

`
from datasets import load_dataset
`
`
dataset = load_dataset("csv", data_files=["./sample_data.csv"], delimiter="\t", column_names=["title", "text"], script_version="master")
`

Displayed error:
`
...
ArrowInvalid: CSV parse error: Expected 2 columns, got 1
`

I should mention that when I've tried to read data from `https://github.com/lhoestq/transformers/tree/custom-dataset-in-rag-retriever/examples/rag/test_data/my_knowledge_dataset.csv` it worked without a problem. I've read that there might be some problems with /r character, so I've removed them from the custom dataset, but the problem still remains.

I've added a colab reproducing the bug, but unfortunately I cannot provide the dataset.
https://colab.research.google.com/drive/1Qzu7sC-frZVeniiWOwzoCe_UHZsrlxu8?usp=sharing

Are there any work around for it ?
Thank you
load_dataset for CSV files not working 
 Similar to #622, I've noticed there is a problem when trying to load a CSV file with datasets.

`
from datasets import load_dataset
`
`
dataset = load_dataset("csv", data_files=["./sample_data.csv"], delimiter="\t", column_names=["title", "text"], script_version="master")
`

Displayed error:
`
...
ArrowInvalid: CSV parse error: Expected 2 columns, got 1
`

I should mention that when I've tried to read data from `https://github.com/lhoestq/transformers/tree/custom-dataset-in-rag-retriever/examples/rag/test_data/my_knowledge_dataset.csv` it worked without a problem. I've read that there might be some problems with /r character, so I've removed them from the custom dataset, but the problem still remains.

I've added a colab reproducing the bug, but unfortunately I cannot provide the dataset.
https://colab.research.google.com/drive/1Qzu7sC-frZVeniiWOwzoCe_UHZsrlxu8?usp=sharing

Are there any work around for it ?
Thank you 
 In this case the user expects to get only one dataset object instead of the dictionary of datasets since only one csv file was specified without any split specifications.
I'm ok with returning the dataset object if no split specifications are given for text/json/csv/pandas.

For the other datasets ton the other hand the user doesn't know in advance the splits so I would keep the dictionary by default. What do you think ?