@ptrblck sorry for straight up pinging you…but do you mind explaining the different btw src_mask vs src_key_padding_mask  (or more generally _mask vs _key_padding_mask)?
My understanding is that everything wrt masking can be done with _mask e.g. if the length of the sequence is T then I can always just mark the padding with a T * T matrix…is that not right?
What are use cases for one vs the other?