[docstring] misc arg doc corrections
Author: stas00
Pull request: yes

- fix docstring s/int/bool/
- correct arg description
- fix num_labels to match reality

Comments:
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/6932?src=pr&el=h1) Report
> Merging [#6932](https://codecov.io/gh/huggingface/transformers/pull/6932?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/e95d262f2553859af9bffbfe5f5bc7e362259939?el=desc) will **increase** coverage by `1.83%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/6932/graphs/tree.svg?width=650&height=150&src=pr&token=9qOlN6Hb1c)](https://codecov.io/gh/huggingface/transformers/pull/6932?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #6932      +/-   ##
==========================================
+ Coverage   77.70%   79.53%   +1.83%     
==========================================
  Files         161      161              
  Lines       30119    30119              
==========================================
+ Hits        23403    23956     +553     
+ Misses       6716     6163     -553     
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/6932?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/configuration\_bart.py](https://codecov.io/gh/huggingface/transformers/pull/6932/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9jb25maWd1cmF0aW9uX2JhcnQucHk=) | `94.00% <ø> (ø)` | |
| [src/transformers/modeling\_tf\_albert.py](https://codecov.io/gh/huggingface/transformers/pull/6932/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl9hbGJlcnQucHk=) | `21.47% <0.00%> (-69.44%)` | :arrow_down: |
| [src/transformers/tokenization\_xlm.py](https://codecov.io/gh/huggingface/transformers/pull/6932/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy90b2tlbml6YXRpb25feGxtLnB5) | `16.26% <0.00%> (-66.67%)` | :arrow_down: |
| [src/transformers/modeling\_tf\_gpt2.py](https://codecov.io/gh/huggingface/transformers/pull/6932/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl9ncHQyLnB5) | `71.84% <0.00%> (-23.17%)` | :arrow_down: |
| [src/transformers/modeling\_xlnet.py](https://codecov.io/gh/huggingface/transformers/pull/6932/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ194bG5ldC5weQ==) | `60.81% <0.00%> (-22.62%)` | :arrow_down: |
| [src/transformers/modeling\_longformer.py](https://codecov.io/gh/huggingface/transformers/pull/6932/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ19sb25nZm9ybWVyLnB5) | `71.55% <0.00%> (-20.48%)` | :arrow_down: |
| [src/transformers/data/data\_collator.py](https://codecov.io/gh/huggingface/transformers/pull/6932/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9kYXRhL2RhdGFfY29sbGF0b3IucHk=) | `86.63% <0.00%> (-6.08%)` | :arrow_down: |
| [src/transformers/modeling\_tf\_xlm.py](https://codecov.io/gh/huggingface/transformers/pull/6932/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl94bG0ucHk=) | `88.42% <0.00%> (-4.85%)` | :arrow_down: |
| [src/transformers/file\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/6932/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9maWxlX3V0aWxzLnB5) | `82.41% <0.00%> (-0.26%)` | :arrow_down: |
| [src/transformers/modeling\_bert.py](https://codecov.io/gh/huggingface/transformers/pull/6932/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ19iZXJ0LnB5) | `88.26% <0.00%> (-0.17%)` | :arrow_down: |
| ... and [9 more](https://codecov.io/gh/huggingface/transformers/pull/6932/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/huggingface/transformers/pull/6932?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/6932?src=pr&el=footer). Last update [e95d262...1c08fdb](https://codecov.io/gh/huggingface/transformers/pull/6932?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).


Thanks. Will in these fixes don't hesitate to replace the True or False by :obj:\`True\` and :obj:\`False\` for consistency (also don't hesitate to tag me on doc PR for quicker reviews :-) )

Understood!

Do we have a model of perhaps one largish module that we can use a reference for how the rest should be done? So that you polish the hell out of it, and then this will be the model to follow.


`tokenization_utils_base` is a good example for instance, all other utils modules too. `config_utils` has an example of how to split parameters in several subgroups if you ever need a model of that. Rules are the usual sphinx-like and some more personal nits are:
- not writing "defaults to :obj:\`None\`" for optional things that have default (it's implied)
- using :obj:\`foo\` syntax for objects (like False, True, all strings) or mention to other arguments
 but not numbers (like 0, 1.0...)
- using italics for optional

Great tips on the model docs and the small specifics. I see some are already here:
https://github.com/huggingface/transformers/tree/master/docs#writing-documentation---specification
add the others too?

Loving params subgroup docs - it's very helpful. I'd organize the params in the function in the same groups too.

Thank you for sharing all these, @sgugger!

Yes we could add those general rules to that section of the docs README. (I am unsure people actually read that so did not take the time to properly update it :-) )

I didn't know it was there, but now that I do, I'd definitely per-use it - so yes, please update it!

>     * not writing "defaults to :obj:`None`" for optional things that have default (it's implied)
```
grep -r "defaults to :obj:.None." src | wc -l
```
```
580
```
might be easy to replace in one swoop.



Feel free to do it in one PR :-)

Done: https://github.com/huggingface/transformers/pull/6956