sendAttachment(type, url, quickReplies, options) {
    return this.bot.sendAttachment(this.userId, type, url, quickReplies, options);
  }
@param {String} type Must be 'image', 'audio', 'video' or 'file'.
@param {String} url URL of the attachment.
@param {Array.<QuickReply>} quickReplies 
@param {SendMessageOptions} options