public function initClient($custom_params = [], $custom_handler = null)
    {
        $config = [
            'base_uri' => $this->getBaseAPIEndpoint(),
            'headers'  => [
                'Accept'               => 'application/json',
                'User-Agent'           => self::USER_AGENT . ' ' . self::CLIENT_VERSION,
                self::APP_TOKEN_HEADER => $this->app_token,
                self::LANG_HEADER      => $this->language,
                self::TIMEZONE_HEADER  => $this->timezone,
                'X-Customer-IP'           => $this->getCustomerIP()
            ]
        ];

        $config = array_merge($config, $custom_params);

        $this->api_client = new ApiRequest($config);
    }