public function add(string $string, float $score, bool $increment = false, $payload = null)
    {
        $args = [
            $this->indexName,
            $string,
            $score
        ];
        if ($increment) {
            $args[] = 'INC';
        }
        if (!is_null($payload)) {
            $args[] = 'PAYLOAD';
            $args[] = $payload;
        }
        return $this->redisClient->rawCommand('FT.SUGADD', $args);
    }