Fix PyTorch 2.3.1 compatibility: add version guard for torch.library.…

[Aishwarya0811]

What does this PR do?

Fixes#12195 by adding version guards for torch.library.custom_op and torch.library.register_fake which are not available in PyTorch 2.3.1.

Problem

• torch.library.custom_op and torch.library.register_fake were introduced in PyTorch 2.4
• Users with PyTorch 2.3.1 get AttributeError: module 'torch.library' has no attribute 'custom_op'
• This breaks from diffusers import AutoencoderKL and other imports

Solution

• Added hasattr() checks before using these torch.library functions
• Functions are only registered when available in the PyTorch version
• Maintains backward compatibility with PyTorch 2.3.1 without breaking newer versions

Testing

• ✅ Tested with PyTorch 2.3.1 - import now works without errors
• ✅ Verified AutoencoderKL imports and functions correctly
• ✅ No regressions expected with newer PyTorch versions

Fixes#12195

Who can review?

@sayakpaul@yiyixuxu - This is a PyTorch compatibility fix for core library functionality.

[a-r-r-o-w]

Hi, thanks for the fix! I think we can improve a bit here by using the approach followed in #11941. Specifically, the following lines:

diffusers/src/diffusers/models/attention_dispatch.py

Lines 121 to 139 in 0018b62

	iftorch.__version__>="2.4.0":
	_custom_op=torch.library.custom_op
	_register_fake=torch.library.register_fake
	else:
	def_custom_op_no_op(name, fn=None, /, *, mutates_args, device_types=None, schema=None):
	defwrap(func):
	returnfunc
	returnwrapiffnisNoneelsefn
	def_register_fake_no_op(op, fn=None, /, *, lib=None, _stacklevel=1):
	defwrap(func):
	returnfunc
	returnwrapiffnisNoneelsefn
	_custom_op=_custom_op_no_op
	_register_fake=_register_fake_no_op

[Aishwarya0811]

Hi @a-r-r-o-w
Thanks for the feedback! I've updated the PR to use the dummy decorator approach as suggested, following the pattern from #11941. The code is much cleaner now without the indentation changes.

Tested with PyTorch 2.3.1 and the import works correctly.

[a-r-r-o-w]

Thanks for the updates! Just one more comment

[Aishwarya0811]

Hi @a-r-r-o-w I've addressed all your feedback - moved the version check to the top of the file and used private naming with underscores.

[a-r-r-o-w]

Thanks for looking into it @Aishwarya0811!

[a-r-r-o-w]

@bot /style

[github-actions]

Style bot fixed some files and pushed the changes.

[HuggingFaceDocBuilderDev]

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