 Split type not preserved when reloading the dataset
{'login': 'mariosasko', 'id': 47462742, 'node_id': 'MDQ6VXNlcjQ3NDYyNzQy', 'avatar_url': 'https://avatars.githubusercontent.com/u/47462742?v=4', 'gravatar_id': '', 'url': 'https://api.github.com/users/mariosasko', 'html_url': 'https://github.com/mariosasko', 'followers_url': 'https://api.github.com/users/mariosasko/followers', 'following_url': 'https://api.github.com/users/mariosasko/following{/other_user}', 'gists_url': 'https://api.github.com/users/mariosasko/gists{/gist_id}', 'starred_url': 'https://api.github.com/users/mariosasko/starred{/owner}{/repo}', 'subscriptions_url': 'https://api.github.com/users/mariosasko/subscriptions', 'organizations_url': 'https://api.github.com/users/mariosasko/orgs', 'repos_url': 'https://api.github.com/users/mariosasko/repos', 'events_url': 'https://api.github.com/users/mariosasko/events{/privacy}', 'received_events_url': 'https://api.github.com/users/mariosasko/received_events', 'type': 'User', 'site_admin': False}
[]
[]
[]
A minimal reproducible example:
```python
>>> from datasets import load_dataset, Dataset
>>> dset = load_dataset("sst", split="train")
>>> dset.save_to_disk("sst")
>>> type(dset.split)
<class 'datasets.splits.NamedSplit'>
>>> dset = Dataset.load_from_disk("sst")
>>> type(dset.split)  # NamedSplit expected
<class 'str'>
```

It seems like this bug was introduced in #2025.
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