Iterate over the stored objects

        Yields:
            wrkey: The two-tuple key used to store the object
            obj: The instance or function object

def iter_instances(self):
        """Iterate over the stored objects

        Yields:
            wrkey: The two-tuple key used to store the object
            obj: The instance or function object
        """
        for wrkey in set(self.keys()):
            obj = self.get(wrkey)
            if obj is None:
                continue
            yield wrkey, obj