Is this bad practice? Overloading methods for generic interface and returning different types

Question

As a follow-up to this question:
Is a bad practice to Return different types when overloading a method?

I am thinking about a very simple mapper interface I'm using:

public interface IMap<T,U>
{
    U MapFrom(T obj);
    T MapFrom(U obj);
}

This is perhaps a more targeted example of the noted question's discussion. An instance implementing this interface just maps between types.
I could do it this way:

public interface IMap<T,U>
{
    U MapRight(T obj);
    T MapLeft(U obj);
}

but that seems silly because, conceptually, the notion of to and from don't really apply to my generic mapper here. It's just a bidirectional map. So, to compliment the linked question:
Is this generic map bad practice?

How should I name methods to avoid returning different types without compromising the "genericness" of the interface?

EDIT: Also, in response to an answer, this is for mapper (not that it's really relevant). I just don't include the mapping method in the interface.

EDIT2: I suppose the same question would apply if I had a single-direction mapper (or adapter) then I implemented it twice for the two directions... same method name, different return type.