Fixed resize_token_embedding issue #21053
Author: susnato
Pull request: yes

# What does this PR do?

There was a typo in Line 449 in [huggingface/transformers/blob/main/src/transformers/models/gpt2/modeling_tf_gpt2.py](https://github.com/huggingface/transformers/blob/48d4e147d824efab97637947709d5aa67c809b3d/src/transformers/models/gpt2/modeling_tf_gpt2.py#L449) where the code was doing a check between input_ids and self.vocab_size but resize_token_embeddings change self.config.vocab_size so we were getting the error described in the issue, to overcome this I replaced it with self.config.vocab_size and it worked. 
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Comments:
_The documentation is not available anymore as the PR was closed or merged._

cc @gante and @Rocketknight1 

@sgugger feel free to merge if you approve. As I wrote above, other models have a similar problem (which require a more elaborate fix)

@susnato can you remove the `Fixes https://github.com/huggingface/transformers/issues/21053` at the top? That way, the issue stays open and I'll likely won't forget to fix the other models :)

> @susnato can you remove the `Fixes https://github.com/huggingface/transformers/issues/21053` at the top? That way, the issue stays open and I'll likely won't forget to fix the other models :)

Hi, @gante I removed the line...is it ok now?

> This is absolutely correct. `self.vocab_size` can easily get stale when the vocabulary gets updated, and the check should be done against the config.
> 
> (there are other models with this issue, where the fix needs to be slightly different, so I'll have a look very soon)

Hi, @gante if you want, I would be happy to look into this and fix if I can.

@susnato sounds good!

My plan consists in removing all references to `self.vocab_size`, deleting the variable whenever it is a variable that is set at `__init__` time from the `config` (if needed, store the `config` in `self.config` instead, since it will hold the mutable vocabulary size).

If you search for "tf.cast(self.vocab_size", you will find all matches that will likely have to be touched.

> @susnato sounds good!
> 
> My plan consists in removing all references to `self.vocab_size`, deleting the variable whenever it is a variable that is set at `__init__` time from the `config` (if needed, store the `config` in `self.config` instead, since it will hold the mutable vocabulary size).
> 
> If you search for "tf.cast(self.vocab_size", you will find all matches that will likely have to be touched.

Hi @gante I am going to check for all models in `src/transformers/models/modeling_tf_<model>.py` to remove references of self.vocab_size and also I found some references of self.vocab_size in some of the  `<model>MLMHead`, I need to change them too right? 

@susnato yes. If we look at the corresponding PT implementation e.g. for Albert, the layer classes store `self.config = config` for future use, as opposed to individual attributes of `config`. Making the switch here protects us from errors like the one that originated this PR :)