How to pass inherited python object back to cpp function correctly

[joeyskeys]

I've defined a cpp class Vec and its corresponding trampoline class PyVec, just like the example from the document and it works fine.
And now there's a function that should takes Vec or perhaps its python inherited object as a parameter, how to make it work successfully on the virtual function(this function also has a python binding)?
A detailed example of the python part is like this:

class AnotherVec(Vec):
     def virtual_func(self):
            do_sth()

v = AnotherVec()
a_binding_func(v)

What I wanna do is to let the python user to define some callback function in python code and then be called in the cpp function.

[balcklive]

got the same question, do you solve it?