update to_py_obj to support np.int type
Author: PrettyMeng
Pull request: yes

# What does this PR do?
Update `to_py_obj` function to make it support np.int type.

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Fixes # See an example below:

>>> tokenizer.decode(110)
'no'
>>> tokenizer.decode(np.array([110])[0])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/prettymeng/anaconda3/envs/ptuning/lib/python3.8/site-packages/transformers/tokenization_utils_base.py", line 3179, in decode
    return self._decode(
  File "/Users/prettymeng/anaconda3/envs/ptuning/lib/python3.8/site-packages/transformers/tokenization_utils_fast.py", line 527, in _decode
    text = self._tokenizer.decode(token_ids, skip_special_tokens=skip_special_tokens)
TypeError: Can't convert 110 to Sequence


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Comments:
> Thanks for your PR! Your check can be improved to use all numpy numeric types. Also, a comment would be welcome as I though `tolist()` would fail on those 0d arrays when it actually succeeds (I though we would need an `item()` for those).

Thanks for the review! Any idea about why this still fails in the test? 

Also, I don't quite understand "a comment would be welcome as I though `tolist()` would fail on those 0d arrays when it actually succeeds (I though we would need an `item()` for those)". 

Do you mean `tolist()` will fail on 0d arrays?

On my own machine, it should work:

>>> np.array(1).tolist()
1

No it does work, but it is surprising as I would not have expected it (since a 0d array is not a "listy" thing). Hence the comment so that when someone else stumbles on this, they are not surprised.

The first failure comes from the code style, run `make style` on your branch to solve it.
The second failure is unrelated to this PR, you can ignore it.

Mmm, it looks like the `make style` command did not properly format. Make sure you do
```
pip install -e .[quality]
```
to have the same versions of all the libraries we use.

> Mmm, it looks like the `make style` command did not properly format. Make sure you do
> 
> ```
> pip install -e .[quality]
> ```
> 
> to have the same versions of all the libraries we use.

I see. Thanks! It should work now.

Mmm, it looks like the PR is now changing 53 files. It may due to a rebase on master, so could you close this PR and open a fresh one from your branch? This way GitHub should only show the real diff.