Add type hints for Whisper models
Author: donelianc
Pull request: yes

# What does this PR do?

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Adding type hints for ` Whisper` model (TensorFlow). Related to the issue #16059.

## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [x] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests), Pull Request section?
- [x] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? _Task requested [here](https://github.com/huggingface/transformers/issues/16059#issuecomment-1324302192)._
- [x] Did you make sure to update the documentation with your changes? Here are the [documentation guidelines](https://github.com/huggingface/transformers/tree/main/docs), and [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [x] Did you write any new necessary tests? _Ran `make fixup` before last commit._


## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

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Models:

- albert, bert, xlm: @LysandreJik
- blenderbot, bart, marian, pegasus, encoderdecoder,  t5: @patrickvonplaten, @patil-suraj
- longformer, reformer, transfoxl, xlnet: @patrickvonplaten
- fsmt: @stas00
- funnel: @sgugger
- gpt2: @patrickvonplaten, @LysandreJik
- rag: @patrickvonplaten, @lhoestq
- tensorflow: @LysandreJik

Library:

- benchmarks: @patrickvonplaten
- deepspeed: @stas00
- ray/raytune: @richardliaw, @amogkam
- text generation: @patrickvonplaten
- tokenizers: @n1t0, @LysandreJik
- trainer: @sgugger
- pipelines: @LysandreJik

Documentation: @sgugger

HF projects:

- datasets: [different repo](https://github.com/huggingface/datasets)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

Examples:

- maintained examples (not research project or legacy): @sgugger, @patil-suraj
- research_projects/bert-loses-patience: @JetRunner
- research_projects/distillation: @VictorSanh

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Comments:
_The documentation is not available anymore as the PR was closed or merged._

Hi @Rocketknight1, can you help me understand failed test? The following [message](https://app.circleci.com/pipelines/github/huggingface/transformers/52274/workflows/ccc607ce-79a5-4b31-a567-22e5e638338b/jobs/626467?invite=true#step-111-353) comes from the CI test logs:

```
You have to specify either decoder_input_ids or decoder_inputs_embeds
```

According to Whisper [documentation](https://huggingface.co/docs/transformers/v4.24.0/en/model_doc/whisper#transformers.TFWhisperForConditionalGeneration.call.past_key_values),

> If decoder_input_ids and decoder_inputs_embeds are both unset, decoder_inputs_embeds takes the value of inputs_embeds.


But, when I checked the argument `inputs_embeds` set for testing, I noticed that `inputs_embeds=None`.
I'm confused because the model had `=None` for all its parameters before I added the type hints.

Hey! I think you are right here, the documentation is misleading. This only happens for the `...ForConditionalGeneration` and not for the model. Opening a PR right now to fix this

@Rocketknight1 this PR is ready for review. 

Besides including the type hints for main Whisper models, I changed the `output_type` to  `TFSeq2SeqModelOutput` in the `TFWhisperModel`'s _docstrings_ since it has a wrong output (probably a confusion with the `TFWhisperForConditionalGeneration` model).