Why is sigmoid activation for LRP not allowed?

[CloseChoice]

❓ Questions and Help

I tried to a small model with a sigmoid activation but it's actually tested here that this does not work. Is there a specific reason for that? IMO since sigmoid is a scalar operation it should work analogously to ReLU and Tanh which can be used with LRP.

Simply adding sigmoid here yields the expected result. So why not just do so?

I would be willing to create the PR and add a test for this if there is no reason not to.