public function getParams(array $overrides = null) {
        $params = array(
            'token' => $this->_token,
            'channel' => $this->_channel,
            'icon_emoji' => $this->_icon_emoji,
            'username' => $this->_username
        );

        if ($overrides) {
            $params = array_merge($params, $overrides);
        }

        return $params;
    }