public static function sendMediaGroup($chat_id = null, $media, $disable_notification = false, $reply_to_message_id = '')
    {
        self::initialize();
        $chat_id = $chat_id ? $chat_id : self::$channel_username;
        $params = compact('chat_id','media', 'disable_notification', 'reply_to_message_id');
        $result = self::sendRequest('sendMediaGroup', $params);
        return $result? $result : false;
    }