Add FluxPAGPipeline with support for PAG

[tongyu0924]

What does this PR do?

This PR adds support for Perturbed Attention Guidance (PAG) to the FluxPipeline

Fixes #11488

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• [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• [ ] Did you write any new necessary tests?

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[DN6]

@tongyu0924 Is this ready for review? If so, could you move the pipeline under src/diffusers/pipelines/pag please and make the changes needed to import the pipeline?

[tongyu0924]

@tongyu0924 Is this ready for review? If so, could you move the pipeline under src/diffusers/pipelines/pag please and make the changes needed to import the pipeline?

Done! The pipeline is now under src/diffusers/pipelines/pag. It's ready for review

[DN6]

Thank you @tongyu0924 👍🏽! Could we add the pipeline to the necessary init files

PAG Module: https://github.com/huggingface/diffusers/blob/main/src/diffusers/pipelines/pag/init.py

Pipelines Module: https://github.com/huggingface/diffusers/blob/049082e013fb71d78f3abf487916f3de2b674908/src/diffusers/pipelines/init.py#L175

Diffusers main init https://github.com/huggingface/diffusers/blob/049082e013fb71d78f3abf487916f3de2b674908/src/diffusers/init.py#L341

And then could you please add a fast test for the pipeline, similar to how it has been done here https://github.com/huggingface/diffusers/blob/049082e013fb71d78f3abf487916f3de2b674908/tests/pipelines/pag/test_pag_sd3.py#L26

[tongyu0924]

Thank you @tongyu0924 👍🏽! Could we add the pipeline to the necessary init files

PAG Module: https://github.com/huggingface/diffusers/blob/main/src/diffusers/pipelines/pag/init.py

Pipelines Module:

https://github.com/huggingface/diffusers/blob/049082e013fb71d78f3abf487916f3de2b674908/src/diffusers/pipelines/init.py#L175

Diffusers main init

https://github.com/huggingface/diffusers/blob/049082e013fb71d78f3abf487916f3de2b674908/src/diffusers/init.py#L341

And then could you please add a fast test for the pipeline, similar to how it has been done here

https://github.com/huggingface/diffusers/blob/049082e013fb71d78f3abf487916f3de2b674908/tests/pipelines/pag/test_pag_sd3.py#L26

I've added the pipeline to the necessary __init__.py files and added a fast test following the structure in test_pag_sd3.py.

[nitinmukesh]

Please update the following if possible

diffusers/src/diffusers/pipelines/pag/pipeline_pag_flux.py

EXAMPLE_DOC_STRING = """ Examples: ```py >>> import torch >>> from diffusers import FluxPipeline

    >>> pipe = FluxPipeline.from_pretrained("black-forest-labs/FLUX.1-schnell", torch_dtype=torch.bfloat16)
    >>> pipe.to("cuda")
    >>> prompt = "A cat holding a sign that says hello world"
    >>> # Depending on the variant being used, the pipeline call will slightly vary.
    >>> # Refer to the pipeline documentation for more details.
    >>> image = pipe(prompt, num_inference_steps=4, guidance_scale=0.0).images[0]
    >>> image.save("flux.png")
    ```

"""

[semioz]

hi, just wanted to check in, are there any updates on when this might be merged?