# Extension method helpers and proof of concept.
import inspect

MODULE_REGISTRY = set()
METHOD_REGISTRY = {}

def get_execution_scope():
    frm = inspect.stack()[2]
    return inspect.getmodule(frm[0])

def extends(cls):
    def inner(func):
        METHOD_REGISTRY.setdefault(cls, set()).add(func)
        return func
    return inner

def using():
    MODULE_REGISTRY.add(get_execution_scope())

class MyObject:
    # Base class that supports extension methods.
    def __getattribute__(self, name):
        try:
            return super().__getattribute__(name)
        except AttributeError:
            mod = get_execution_scope()
            if mod in MODULE_REGISTRY:
                xmethods = METHOD_REGISTRY.get(type(self), set())
                for func in xmethods:
                    if func.__name__ == name:
                        return func.__get__(self)
            raise

class Demo(MyObject):
    pass

@extends(Demo)
def xmethod(self):
    return "called extension method"