Use ndarray.item instead of ndarray.tolist
{'login': 'lewtun', 'id': 26859204, 'node_id': 'MDQ6VXNlcjI2ODU5MjA0', 'avatar_url': 'https://avatars.githubusercontent.com/u/26859204?v=4', 'gravatar_id': '', 'url': 'https://api.github.com/users/lewtun', 'html_url': 'https://github.com/lewtun', 'followers_url': 'https://api.github.com/users/lewtun/followers', 'following_url': 'https://api.github.com/users/lewtun/following{/other_user}', 'gists_url': 'https://api.github.com/users/lewtun/gists{/gist_id}', 'starred_url': 'https://api.github.com/users/lewtun/starred{/owner}{/repo}', 'subscriptions_url': 'https://api.github.com/users/lewtun/subscriptions', 'organizations_url': 'https://api.github.com/users/lewtun/orgs', 'repos_url': 'https://api.github.com/users/lewtun/repos', 'events_url': 'https://api.github.com/users/lewtun/events{/privacy}', 'received_events_url': 'https://api.github.com/users/lewtun/received_events', 'type': 'User', 'site_admin': False}
[]
[]
This PR follows up on #2612 to use `numpy.ndarray.item` instead of `numpy.ndarray.tolist` as the latter is somewhat confusing to the developer (even though it works).

Judging from the `numpy` docs, `ndarray.item` is closer to what we want: https://numpy.org/doc/stable/reference/generated/numpy.ndarray.item.html#numpy-ndarray-item

PS. Sorry for the duplicate work here. I should have read the numpy docs more carefully in #2612 

{'url': 'https://api.github.com/repos/huggingface/datasets/issues/2613/reactions', 'total_count': 0, '+1': 0, '-1': 0, 'laugh': 0, 'hooray': 0, 'confused': 0, 'heart': 0, 'rocket': 0, 'eyes': 0}
{'url': 'https://api.github.com/repos/huggingface/datasets/pulls/2613', 'html_url': 'https://github.com/huggingface/datasets/pull/2613', 'diff_url': 'https://github.com/huggingface/datasets/pull/2613.diff', 'patch_url': 'https://github.com/huggingface/datasets/pull/2613.patch', 'merged_at': '2021-07-09T13:50:05Z'}