Throw an error when dataset improperly indexed
MEMBER
Thanks for reporting, @sarahwie.

Please note that in `datasets` we do not have vectorized operation like `pandas`. Therefore, your equality comparisons above are `False`:
- For example: `squad['question']` returns a `list`, and this list is not equal to `"Who was the Norse leader?"`

The `False` value is equivalent to `0` when indexing a dataset, thus the reason why you get the first element (with index 0): 
- For example: `squad[False]` is equivalent to `squad[0]`

Maybe we should an exception instead of assuming that `False` is equivalent to `0` (and `True` is equivalent to `1`) in the context of indexing.
2023-05-15T07:15:08Z
https://github.com/huggingface/datasets/issues/5858#issuecomment-1547312692
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2023-05-15T07:15:08Z
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### Describe the bug

Pandas-style subset indexing on dataset does not throw an error, when maybe it should. Instead returns the first instance of the dataset regardless of index condition.

### Steps to reproduce the bug

Steps to reproduce the behavior:

1. `squad = datasets.load_dataset("squad_v2", split="validation")`
2. `item = squad[squad['question'] ==  "Who was the Norse leader?"]`
or `it = squad[squad['id'] == '56ddde6b9a695914005b962b']`
3.  returns the first item in the dataset, which does not satisfy the above conditions:

`{'id': '56ddde6b9a695914005b9628', 'title': 'Normans', 'context': 'The Normans (Norman: Nourmands; French: Normands; Latin: Normanni) were the people who in the 10th and 11th centuries gave their name to Normandy, a region in France. They were descended from Norse ("Norman" comes from "Norseman") raiders and pirates from Denmark, Iceland and Norway who, under their leader Rollo, agreed to swear fealty to King Charles III of West Francia. Through generations of assimilation and mixing with the native Frankish and Roman-Gaulish populations, their descendants would gradually merge with the Carolingian-based cultures of West Francia. The distinct cultural and ethnic identity of the Normans emerged initially in the first half of the 10th century, and it continued to evolve over the succeeding centuries.', 'question': 'In what country is Normandy located?', 'answers': {'text': ['France', 'France', 'France', 'France'], 'answer_start': [159, 159, 159, 159]}}`

### Expected behavior

Should either throw an error message, or return the dataset item that satisfies the condition.

### Environment info

- `datasets` version: 2.9.0
- Platform: macOS-13.3.1-arm64-arm-64bit
- Python version: 3.10.8
- PyArrow version: 10.0.1
- Pandas version: 1.5.3