public function isMember($member): bool
    {
        return $this->redis->sismember($this->key, $this->serialize($member)) === self::RESPONSE_SUCCESS;
    }
public function isMember($member): bool
    {
        return $this->redis->sismember($this->key, $this->serialize($member)) === self::RESPONSE_SUCCESS;
    }
@param mixed $member Member to look for.

@return bool True if $member is in set. False otherwise.