redisPushFn *redisSetPushCallback(redisContext *c, redisPushFn *fn) {
    redisPushFn *old = c->push_cb;
    c->push_cb = fn;
    return old;
}
redisPushFn *redisSetPushCallback(redisContext *c, redisPushFn *fn) {
    redisPushFn *old = c->push_cb;
    c->push_cb = fn;
    return old;
}