[dataset] Structure of MLQA seems unecessary nested
MEMBER
Same for the RACE dataset: https://github.com/huggingface/nlp/blob/master/datasets/race/race.py

Should we scan all the datasets to remove this pattern of un-necessary nesting?
2020-07-11T15:19:15Z
https://github.com/huggingface/datasets/issues/378#issuecomment-657079719
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CONTRIBUTOR
You're right, I think we don't need to use the nested dictionary. 

2020-07-13T08:34:28Z
https://github.com/huggingface/datasets/issues/378#issuecomment-657408805
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The features of the MLQA dataset comprise several nested dictionaries with a single element inside (for `questions` and `ids`): https://github.com/huggingface/nlp/blob/master/datasets/mlqa/mlqa.py#L90-L97

Should we keep this @mariamabarham @patrickvonplaten? Was this added for compatibility with tfds?

```python
            features=nlp.Features(
                {
                    "context": nlp.Value("string"),
                    "questions": nlp.features.Sequence({"question": nlp.Value("string")}),
                    "answers": nlp.features.Sequence(
                        {"text": nlp.Value("string"), "answer_start": nlp.Value("int32"),}
                    ),
                    "ids": nlp.features.Sequence({"idx": nlp.Value("string")})
```