Add `features` param to `IterableDataset.map`
NONE
_The documentation is not available anymore as the PR was closed or merged._
2022-11-29T11:13:45Z
https://github.com/huggingface/datasets/pull/5311#issuecomment-1330466830
https://api.github.com/repos/huggingface/datasets/issues/5311
IC_kwDODunzps5PTVAO
https://api.github.com/repos/huggingface/datasets/issues/comments/1330466830/reactions
2022-12-06T15:45:01Z
https://api.github.com/repos/huggingface/datasets/issues/comments/1330466830
https://avatars.githubusercontent.com/u/99929124?v=4
https://api.github.com/users/HuggingFaceDocBuilderDev/events{/privacy}
https://api.github.com/users/HuggingFaceDocBuilderDev/followers
https://api.github.com/users/HuggingFaceDocBuilderDev/following{/other_user}
https://api.github.com/users/HuggingFaceDocBuilderDev/gists{/gist_id}
https://github.com/HuggingFaceDocBuilderDev
HuggingFaceDocBuilderDev
U_kgDOBfTMJA
https://api.github.com/users/HuggingFaceDocBuilderDev/orgs
https://api.github.com/users/HuggingFaceDocBuilderDev/received_events
https://api.github.com/users/HuggingFaceDocBuilderDev/repos
https://api.github.com/users/HuggingFaceDocBuilderDev/starred{/owner}{/repo}
https://api.github.com/users/HuggingFaceDocBuilderDev/subscriptions
User
https://api.github.com/users/HuggingFaceDocBuilderDev
public
## Description

As suggested by @lhoestq in #3888, we should be adding the param `features` to `IterableDataset.map` so that the features can be preserved (not turned into `None` as that's the default behavior) whenever the user passes those as param, so as to be consistent with `Dataset.map`, as it provides the `features` param so that those are not inferred by default, but specified by the user, and later validated by `ArrowWriter`.

This is internally handled already by the functions relying on `IterableDataset.map` such as `rename_column`, `rename_columns`, and `remove_columns` as described in #5287.

## Usage Example

```python
from datasets import load_dataset, Features

ds = load_dataset("rotten_tomatoes", split="validation", streaming=True)
print(ds.info.features)
ds = ds.map(
    lambda x: {"target": x["label"]},
    features=Features(
        {"target": ds.info.features["label"], "label": ds.info.features["label"], "text": ds.info.features["text"]}
    ),
)
print(ds.info.features)
```