Seeking Guidance: Best Practices for Replacing Default Blocks with Custom Modules in Diffusers' UNet2DModel

[Anonn-798]

Hi Diffusers Community,

I'm currently working on a project where I've successfully implemented a DDPM using the diffusers library. My next step involves customizing the U-Net architecture, specifically the UNet2DModel.

I'm looking to replace some of the default blocks within the UNet2DModel (e.g., ResnetBlock2D, AttentionBlock, or other standard down/up blocks) with my own custom-designed PyTorch modules. My goal is to experiment with novel architectural components tailored for my specific signal processing research while still leveraging the robustness and convenience of the Diffusers framework.

My core question is: What are the recommended approaches or best practices for achieving this kind of modification?

More specifically:

Integration Strategy: How can I effectively swap out a default block in the UNet2DModel's forward pass or definition with a custom torch.nn.Module? For example, if I have a MyCustomResBlock(in_channels, out_channels, temb_channels, ...) or MyCustomAttentionBlock(...), what's the cleanest way to integrate it into the existing U-Net structure, ensuring that tensor shapes and conditioning (like time embeddings) are handled correctly?
Subclassing vs. Modifying Instances: Would it be better to subclass UNet2DModel and override specific methods or block instantiations, or is there a more straightforward way to modify a pre-existing UNet2DModel instance?
Compatibility Concerns: Are there any particular considerations I should keep in mind to ensure that my modified U-Net remains compatible with the rest of the Diffusers pipeline, such as the schedulers, training loops, and inference mechanisms?
Pointers to Examples/Docs: If there are any existing examples, documentation snippets, or community discussions that touch upon similar U-Net customizations within Diffusers, I would be very grateful for a pointer.
I've explored the source code of UNet2DModel to understand its structure, but I'd appreciate insights from experienced users or developers on how to make these changes in a maintainable and effective way.

Thank you in advance for any guidance or suggestions you can offer!

Best regards,