Can `LayerInfo.depth_index` really be `None`?

[ego-thales]

Hello !

Not sure this is actually an "issue".

I was wondering if there any use cases where a LayerInfo.depth_index from a summary_list could be None?
Because it is typed as follows and may raise type checking issue when considering it can be None.

torchinfo/torchinfo/layer_info.py

Line 47 in 890def3

self.depth_index: int | None = None # set at the very end

Of course it is easy to monkey patch by checking for None and eventually cast (even though mypy generally understands by itself the disjunction). Still, if it never arisses, it seems a bit weird to do it on the user side and not inside torchinfo.

Thanks!