duplicated line for repeating_words_penalty_for_language_generation
length_penalty has a duplicated wrong documentation for language generation -> delete two lines
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/2290?src=pr&el=h1) Report
> Merging [#2290](https://codecov.io/gh/huggingface/transformers/pull/2290?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/aeef4823ab6099249679756182700e6800024c36?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `0%`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/2290/graphs/tree.svg?width=650&token=9qOlN6Hb1c&height=150&src=pr)](https://codecov.io/gh/huggingface/transformers/pull/2290?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #2290      +/-   ##
==========================================
- Coverage   73.49%   73.48%   -0.01%     
==========================================
  Files          87       87              
  Lines       14793    14794       +1     
==========================================
  Hits        10872    10872              
- Misses       3921     3922       +1
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/2290?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/modeling\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/2290/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ191dGlscy5weQ==) | `63.34% <0%> (-0.12%)` | :arrow_down: |

------

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> **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/2290?src=pr&el=footer). Last update [aeef482...0f6017b](https://codecov.io/gh/huggingface/transformers/pull/2290?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
<|||||>Yes, actually the doc is still not complete for this new feature.

We should add some examples and double-check all. Feel free to clean this up if you feel like it.<|||||>clean up documentation, add examples for documentation and rename some variables<|||||>checked example generation for openai-gpt, gpt2, xlnet and xlm in combination with #2289.
<|||||>Also checked for ctrl<|||||>also checked for transfo-xl<|||||>Awesome, merging!