getChatMember(chatId, userId, form = {}) {
    form.chat_id = chatId;
    form.user_id = userId;
    return this._request('getChatMember', { form });
  }
Use this method to get information about a member of a chat.

@param {Number|String} chatId  Unique identifier for the target group or username of the target supergroup
@param {Number} userId  Unique identifier of the target user
@param {Object} [options] Additional Telegram query options
@return {Promise} [ChatMember](https://core.telegram.org/bots/api#chatmember) object on success
@see https://core.telegram.org/bots/api#getchatmember