sendAudio(chatId, audio, options = {}, fileOptions = {}) {
    const opts = {
      qs: options
    };

    opts.qs.chat_id = chatId;

    try {
      const sendData = this._formatSendData('audio', audio, fileOptions);
      opts.formData = sendData[0];
      opts.qs.audio = sendData[1];
      this._fixAddFileThumbnail(options, opts);
    } catch (ex) {
      return Promise.reject(ex);
    }

    return this._request('sendAudio', opts);
  }
Send audio

**Your audio must be in the .MP3 or .M4A format.**

@param {Number|String} chatId  Unique identifier for the target chat or username of the target channel (in the format `@channelusername`)
@param {String|stream.Stream|Buffer} audio A file path, Stream or Buffer.
Can also be a `file_id` previously uploaded.
@param {Object} [options] Additional Telegram query options
@param {Object} [fileOptions] Optional file related meta-data
@return {Promise} On success, the sent [Message](https://core.telegram.org/bots/api#message) object is returned
@see https://core.telegram.org/bots/api#sendaudio
@see https://github.com/yagop/node-telegram-bot-api/blob/master/doc/usage.md#sending-files