Explanation of the code "cldm/cldm.py": ControlledUnetModel class

[HyeonHo99]

Thank you for amazing works first.

I have read your paper and have been looking at the implementation, especially the cldm.py There's one thing I failed to understand that is (I assume) not specified on the paper.

In the ControlledUnetModel class, in the middle of the code definition, there is

if control is not None: h += control.pop()

So, If a control tensor is provided, it adds it to the output of the middle block? control must mean, for example, edge map feature maps. But why is it added to the output of the middle block?

Thank you.