Can't import Blip2Processor
### System Info

I was trying to follow [this tutorial](https://huggingface.co/docs/transformers/main/en/model_doc/blip-2#transformers.Blip2Model.forward.example) and ran into the following issue:
```
ImportError: cannot import name 'Blip2Processor' from 'transformers' (/usr/local/lib/python3.8/dist-packages/transformers/__init__.py)
```

version: '4.26.1'

@sgugger @ArthurZucker @amyeroberts (there is no PIC for multimodal models so tagging both PICs)

### Who can help?

_No response_

### Information

- [X] The official example scripts
- [ ] My own modified scripts

### Tasks

- [X] An officially supported task in the `examples` folder (such as GLUE/SQuAD, ...)
- [ ] My own task or dataset (give details below)

### Reproduction

Just run the following example: https://huggingface.co/docs/transformers/main/en/model_doc/blip-2#transformers.Blip2Model.forward.example

### Expected behavior

Should import the preprocessor
You need to install transformers from source to get access to BLIP-2:
```
pip install git+https://github.com/huggingface/transformers
```<|||||>@sgugger thank you! Just one minor feedback since you are the docs PIC, if a note modal or just a highlighted note could be added informing if a module hasn't been added to the stable release would be helpful. (If it is already there, I might have missed it, apologies.)<|||||>Note that it's not in the [stable documentation](https://huggingface.co/docs/transformers/index) (which is what is viewed by default) only the [main documentation](https://huggingface.co/docs/transformers/main/en/index). Did you get on the page via a search engine maybe and did not realize you were not on the documentation of the latest release?<|||||>> Note that it's not in the [stable documentation](https://huggingface.co/docs/transformers/index) (which is what is viewed by default) only the [main documentation](https://huggingface.co/docs/transformers/main/en/index). Did you get on the page via a search engine maybe and did not realize you were not on the documentation of the latest release?

I am not the author but this is exactly what happened to me - I did not see at all there's a dropdown for versions so I assumed BLIP2 is just available.