def METHOD_NAME(self, subject_id, entity_id, ava):
    res = self._cache.get(_key(subject_id, entity_id))
    if res is None:
        raise KeyError("No such subject")
    else:
        info = self.get_info(res)
        if info:
            info.METHOD_NAME(ava)
            self.set(subject_id, entity_id, info, res[0])