addStickerToSet(userId, name, sticker, emojis, stickerType = 'png_sticker', options = {}, fileOptions = {}) {
    const opts = {
      qs: options,
    };
    opts.qs.user_id = userId;
    opts.qs.name = name;
    opts.qs.emojis = emojis;
    opts.qs.mask_position = stringify(options.mask_position);

    if (typeof stickerType !== 'string' || ['png_sticker', 'tgs_sticker', 'webm_sticker'].indexOf(stickerType) === -1) {
      return Promise.reject(new Error('stickerType must be a string and the allow types is: png_sticker, tgs_sticker, webm_sticker'));
    }

    try {
      const sendData = this._formatSendData(stickerType, sticker, fileOptions);
      opts.formData = sendData[0];
      opts.qs[stickerType] = sendData[1];
    } catch (ex) {
      return Promise.reject(ex);
    }
    return this._request('addStickerToSet', opts);
  }
Use this method to add a new sticker to a set created by the bot.

You must use exactly one of the fields *png_sticker*, *tgs_sticker*, or *webm_sticker*

Animated stickers can be added to animated sticker sets and only to them

Note:
- Emoji sticker sets can have up to 200 sticker
- Static or Animated sticker sets can have up to 120 stickers

@param {Number} userId User identifier of sticker set owner
@param {String} name Sticker set name
@param {String|stream.Stream|Buffer} sticker Png image with the sticker (must be up to 512 kilobytes in size,
dimensions must not exceed 512px, and either width or height must be exactly 512px, [TGS animation](https://core.telegram.org/stickers#animated-sticker-requirements)
with the sticker or [WEBM video](https://core.telegram.org/stickers#video-sticker-requirements) with the sticker.
@param {String} emojis One or more emoji corresponding to the sticker
@param {String} stickerType Allow values: `png_sticker`, `tgs_sticker`, or `webm_sticker`.
@param {Object} [options] Additional Telegram query options
@param {Object} [fileOptions] Optional file related meta-data
@return {Promise}  True on success
@see https://core.telegram.org/bots/api#addstickertoset