def __call__(self):
        """Return a strong reference to the bound method

        If the target cannot be retrieved, then will
        return None, otherwise returns a bound instance
        method for our object and function.

        Note:
            You may call this method any number of times,
            as it does not invalidate the reference.
        """
        target = self.weakSelf()
        if target is not None:
            function = self.weakFunc()
            if function is not None:
                return function.__get__(target)
        return None
Return a strong reference to the bound method

        If the target cannot be retrieved, then will
        return None, otherwise returns a bound instance
        method for our object and function.

        Note:
            You may call this method any number of times,
            as it does not invalidate the reference.
        
stackoverflow/venv/lib/python3.6/site-packages/pydispatch/saferef.py