setStickerSetThumbnail(userId, name, thumbnail, options = {}, fileOptions = {}) {
    const opts = {
      qs: options,
    };
    opts.qs.user_id = userId;
    opts.qs.name = name;
    opts.qs.mask_position = stringify(options.mask_position);
    try {
      const sendData = this._formatSendData('thumbnail', thumbnail, fileOptions);
      opts.formData = sendData[0];
      opts.qs.thumbnail = sendData[1];
    } catch (ex) {
      return Promise.reject(ex);
    }
    return this._request('setStickerSetThumbnail', opts);
  }
Use this method to add a thumb to a set created by the bot.

Animated thumbnails can be set for animated sticker sets only. Video thumbnails can be set only for video sticker sets only

@param {Number} userId User identifier of sticker set owner
@param {String} name Sticker set name
@param {String|stream.Stream|Buffer} thumbnail A .WEBP or .PNG image with the thumbnail,
must be up to 128 kilobytes in size and have width and height exactly 100px,
a TGS animation with the thumbnail up to 32 kilobytes in size or a WEBM video with the thumbnail up to 32 kilobytes in size.

Pass a file_id as a String to send a file that already exists on the Telegram servers, pass an HTTP URL as a String for Telegram
to get a file from the Internet, or upload a new one. Animated sticker set thumbnails can't be uploaded via HTTP URL.
@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#setstickersetthumbnail