Add parameter `preserve_index` to `from_pandas`
CONTRIBUTOR
> 

I did `make style` and it affected over 500 files

```
All done! ✨ 🍰 ✨
575 files reformatted, 372 files left unchanged.
isort tests src benchmarks datasets/**/*.py metri
```

(result)
![image](https://user-images.githubusercontent.com/20703486/149166681-2f9d1bc4-116a-4f53-ad42-e54e3b8bd605.png)

2022-01-12T15:09:29Z
https://github.com/huggingface/datasets/pull/3565#issuecomment-1011142365
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2022-01-12T15:10:26Z
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CONTRIBUTOR
Nvm I was using wrong black version
2022-01-12T15:20:29Z
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Added optional parameter, so that user can get rid of useless index preserving. [Issue](https://github.com/huggingface/datasets/issues/3563)