Recursive behavior of can_be_deleted()

I think that the behavior of can_be_deleted(), at least on Libraries is not 100% correct. An object can be deleted if it is not used by another object. So, I think the straightfoward way to check for it would be to just verify if any algorithm is using that library. If that is the case, it cannot be deleted. Else, if nobody references this library, then it can be deleted.

Could you please confirm?