unbanChatMember(chatId, userId, form = {}) {
    form.chat_id = chatId;
    form.user_id = userId;
    return this._request('unbanChatMember', { form });
  }
Use this method to unban a previously kicked user in a supergroup.
The user will not return to the group automatically, but will be
able to join via link, etc.

The **bot must be an administrator** in the supergroup or channel for this to work.

**By default**, this method guarantees that after the call the user is not a member of the chat, but will be able to join it.
So **if the user is a member of the chat they will also be removed from the chat**. If you don't want this, use the parameter *only_if_banned*

@param {Number|String} chatId   Unique identifier for the target chat or username of the target channel (in the format `@channelusername`)
@param {Number} userId  Unique identifier of the target user
@param {Object} [options] Additional Telegram query options
@return {Promise} True on success
@see https://core.telegram.org/bots/api#unbanchatmember