Swap this config with another.

        This is used by the unit tests to swap the config to one that is
        shielded from any user config updates. Do not use this method unless
        you have good reason.

def _swap(self, other):
        """Swap this config with another.

        This is used by the unit tests to swap the config to one that is
        shielded from any user config updates. Do not use this method unless
        you have good reason.
        """
        self.__dict__, other.__dict__ = other.__dict__, self.__dict__