Function Overloading and Python

[Allen Peloquin]

I have a personal project that has an elegant solution that requires
both true multiple inheritance of classes (which pretty much limits my
language choices to C++ and Python) and type-based function
overloading.

Now, while this makes it sound like I have to resign myself to C++,
which I am not a fan of writing, I have resisted thus far. Who wants
to manage their own memory? No, I have fallen in love with Python, and
so come asking for help.

I have a very large multiple inheritance tree that will be frequently
extended as my project goes on. Let us call these "type A" classes.

I also have a moderately sized single inheritance tree whose task is
to match sets of "type A" parameters in a function. Let us call these
"type B" classes. "Type Bs" have one function, which is extended with
each new child, and overloaded to match varying combinations of "Type
As." The reason for this is code-reuse and eventual matching with
common "type A" parents.

Now, what are my options in Python to dispatch unique code based on
the permutations of "type A" classes without code repetition?
Such as, where in C++...

class B
{
    fun(A x, A y, A z)...
    fun(A1 x, A y, A z)...
}

class B1
{
    fun(A1 x, A y, A z)...
}

Such that any previous behavior is inherited, but behaves
polymorphically because of the single function name.

B1.fun(A(x), A(y), A(z)) == B.fun(A(x), A(y), A(z))
but
B1.fun(A1(x), A(y), A(z) != B.fun(A1(x), A(y), A(z))

Is there a data-structure solution or third party module that would
mimic this behavior?

PEP 3124 got my hopes up, but I was let down when it was deferred.

Thank you for your time.