fix #878
# [Codecov](https://codecov.io/gh/huggingface/pytorch-transformers/pull/879?src=pr&el=h1) Report
> Merging [#879](https://codecov.io/gh/huggingface/pytorch-transformers/pull/879?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/pytorch-transformers/commit/067923d3267325f525f4e46f357360c191ba562e?src=pr&el=desc) will **decrease** coverage by `0.01%`.
> The diff coverage is `0%`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/pytorch-transformers/pull/879/graphs/tree.svg?width=650&token=9qOlN6Hb1c&height=150&src=pr)](https://codecov.io/gh/huggingface/pytorch-transformers/pull/879?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master     #879      +/-   ##
==========================================
- Coverage   79.03%   79.02%   -0.02%     
==========================================
  Files          34       34              
  Lines        6234     6235       +1     
==========================================
  Hits         4927     4927              
- Misses       1307     1308       +1
```


| [Impacted Files](https://codecov.io/gh/huggingface/pytorch-transformers/pull/879?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pytorch\_transformers/tokenization\_utils.py](https://codecov.io/gh/huggingface/pytorch-transformers/pull/879/diff?src=pr&el=tree#diff-cHl0b3JjaF90cmFuc2Zvcm1lcnMvdG9rZW5pemF0aW9uX3V0aWxzLnB5) | `86.17% <0%> (-0.36%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/huggingface/pytorch-transformers/pull/879?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/pytorch-transformers/pull/879?src=pr&el=footer). Last update [067923d...31bc1dd](https://codecov.io/gh/huggingface/pytorch-transformers/pull/879?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
<|||||>Closing this for now. Feel free to re-open if you want to continue with this PR.