Documentation in CTRL linksto 404
In https://huggingface.co/docs/transformers/master/en/model_doc/ctrl#overview, when clicking "See reusing the past in generative models", the user is redirected to a 404 (https://huggingface.co/docs/transformers/master/en/quickstart#using-the-past)
Nice catch! @stevhliu, would you like to take a look at that?<|||||>Looks like a [throwback](https://huggingface.co/transformers/v2.2.0/quickstart.html) to `transformers 2.2.0`! Should we point the user to [`CTRLModel.forward()`](https://huggingface.co/docs/transformers/master/en/model_doc/ctrl#transformers.CTRLModel.forward.past_key_values) where they can get more information about the parameter? It looks like I can also update it to say PyTorch accepts `past_key_values` and TF accepts `past`.

Another option could be to also add a code example in [`CTRLModel`](https://huggingface.co/docs/transformers/master/en/model_doc/ctrl#transformers.CTRLModel).<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) are likely to be ignored.<|||||>What you propose sounds good to me @stevhliu!<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) are likely to be ignored.<|||||>This is now fixed after #15615 