RuntimeError: One of the differentiated Tensors appears to not have been used in the graph.

[pILLOW-1]

Hi, when I use BoxDiff, an error about grad appears at _update_latent function:
"RuntimeError: One of the differentiated Tensors appears to not have been used in the graph. Set allow_unused=True if this is the desired behavior"

But when I set allow_unused=True, another error occurs:

Do you have any idea about this? Thanks!