private function attachAgent(): void
    {
        $this->agentName = strtolower((string) $this->config['agent']);
        switch ($this->agentName) {
            case self::AGENT_MYSQL:
                $this->agent = new Mysql($this->config);
                break;
            case self::AGENT_PGSQL:
                $this->agent = new Pgsql($this->config);
                break;
            default:
                throw new LinkException("Sorry, but '{$this->agentName}' agent not implemented!");
        }
    }