Setup Callable attributes that belong to this object.

def setup_callables(self):
        """
            Setup Callable attributes that belong to this object.
        """
        defaults = self.get_default_callables()
        for key, value in list(defaults.items()):
            self._postponed_callables.setdefault(key, value)
        for key in self.callables:
            value = self._postponed_callables.pop(key)
            value.setup_callable_system(self.system, init=True)
            setattr(self, key, value)