newproxy.py

def Proxy:
    """Pass over a callback but get ahold of it
    """
    def __init__(self, callback=None):

        def augmented_call(*args, **kwargs):
            self.callback_notification()
            return callback(*args, **kwargs) if callback else None

        self.someInstance = SomeClass(callback=augmented_call)

    def callback_notification(self):
        print("callback was invoked")

proxy.py

def Proxy:
    """Pass over a callback but get ahold of it
    """
    def __init__(self, callback=None):
        def augmented_call(*args, **kwargs):
            self.callback_notification()
            return callback(*args, **kwargs)

        def empty_callback(*args, **kwargs):
            self.callback_notification()

        self.someInstance = SomeClass(
            callback=augmented_call if callback else empty_callback)

    def callback_notification(self):
        print("callback was invoked")