make shape verification to use ArrayXD instead of nested lists for map
{'login': 'tshu-w', 'id': 13161779, 'node_id': 'MDQ6VXNlcjEzMTYxNzc5', 'avatar_url': 'https://avatars.githubusercontent.com/u/13161779?v=4', 'gravatar_id': '', 'url': 'https://api.github.com/users/tshu-w', 'html_url': 'https://github.com/tshu-w', 'followers_url': 'https://api.github.com/users/tshu-w/followers', 'following_url': 'https://api.github.com/users/tshu-w/following{/other_user}', 'gists_url': 'https://api.github.com/users/tshu-w/gists{/gist_id}', 'starred_url': 'https://api.github.com/users/tshu-w/starred{/owner}{/repo}', 'subscriptions_url': 'https://api.github.com/users/tshu-w/subscriptions', 'organizations_url': 'https://api.github.com/users/tshu-w/orgs', 'repos_url': 'https://api.github.com/users/tshu-w/repos', 'events_url': 'https://api.github.com/users/tshu-w/events{/privacy}', 'received_events_url': 'https://api.github.com/users/tshu-w/received_events', 'type': 'User', 'site_admin': False}
[{'id': 1935892871, 'node_id': 'MDU6TGFiZWwxOTM1ODkyODcx', 'url': 'https://api.github.com/repos/huggingface/datasets/labels/enhancement', 'name': 'enhancement', 'color': 'a2eeef', 'default': True, 'description': 'New feature or request'}]
[]
Hi! 

Yes, this makes sense for numeric values, but first I have to finish https://github.com/huggingface/datasets/pull/3336 because currently ArrayXD only allows the first dimension to be dynamic.
As describe in https://github.com/huggingface/datasets/issues/2005#issuecomment-793716753 and mentioned by @mariosasko in [image feature example](https://colab.research.google.com/drive/1mIrTnqTVkWLJWoBzT1ABSe-LFelIep1c#scrollTo=ow3XHDvf2I0B&line=1&uniqifier=1), IMO make shape verifcaiton to use ArrayXD instead of nested lists for map can help user reduce unnecessary cast. I notice datasets have done something special for `input_ids` and `attention_mask` which is also unnecessary after this feature added.
{'url': 'https://api.github.com/repos/huggingface/datasets/issues/3484/reactions', 'total_count': 0, '+1': 0, '-1': 0, 'laugh': 0, 'hooray': 0, 'confused': 0, 'heart': 0, 'rocket': 0, 'eyes': 0}