Clarification on mutually exclusive use of self-attention and cross-attention in DiffusionModelUNetMaisi

Hi MONAI team,

while reading through the implementation of DiffusionModelUNetMaisi, I noticed the following logic for enabling attention at each level:

with_attn = attention_levels[i] and not with_conditioning
with_cross_attn = attention_levels[i] and with_conditioning

This effectively means that self-attention is never used when the model is in conditioning mode (with_conditioning=True), even if attention_levels[i] is True.

Is this behavior intentional?

In other diffusion-based architectures such as Stable Diffusion, it is common practice to enable both self-attention and cross-attention simultaneously within the same layers.

Would it be acceptable, or even recommended, to modify the logic as follows to allow both mechanisms in parallel?
Or is there a specific reason this mutual exclusivity was enforced?

Looking forward to your insights, and thank you for the great work on this model!

Best regards,
Daniele Molino