Add model tag
Add model tag to be correctly indexed while working on card description
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/3709?src=pr&el=h1) Report
> Merging [#3709](https://codecov.io/gh/huggingface/transformers/pull/3709?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/6435b9f908e7361330db89e263a65b0a58060d11&el=desc) will **decrease** coverage by `0.00%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/3709/graphs/tree.svg?width=650&height=150&src=pr&token=9qOlN6Hb1c)](https://codecov.io/gh/huggingface/transformers/pull/3709?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #3709      +/-   ##
==========================================
- Coverage   78.13%   78.12%   -0.01%     
==========================================
  Files         104      104              
  Lines       17723    17723              
==========================================
- Hits        13847    13846       -1     
- Misses       3876     3877       +1     
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/3709?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/modeling\_tf\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/3709/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl91dGlscy5weQ==) | `92.79% <0.00%> (-0.17%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/huggingface/transformers/pull/3709?src=pr&el=continue).
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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/3709?src=pr&el=footer). Last update [6435b9f...be477cf](https://codecov.io/gh/huggingface/transformers/pull/3709?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
