Returns true if mod is a subclass of other. Returns nil if there’s no relationship between the two. (Think of the relationship in terms of the class definition: “class A<B” implies “A<B”).

Returns true if mod is a subclass of other or is the same as other. Returns nil if there’s no relationship between the two. (Think of the relationship in terms of the class definition: “class A<B” implies “A<B”).