def METHOD_NAME(self, volume_name):
    vol = self.get_volume_user_info(volume_name)
    if vol.mother is None or vol.mother == self.world_name:
        return self.world_name
    if vol.mother in self.parallel_world_names:
        return vol.mother
    if volume_name not in self.volumes_user_info:
        gate.fatal(f"Cannot find the volume {volume_name}")
    return self.METHOD_NAME(vol.mother)