leaveGroup(groupId, callback) {
		return StdLib.Promises.timeoutCallbackPromise(10000, null, callback, true, (resolve, reject) => {
			this.user._sendUnified('ChatRoom.LeaveChatRoomGroup#1', {
				chat_group_id: groupId
			}, (body, hdr) => {
				let err = Helpers.eresultError(hdr.proto);
				if (err) {
					return reject(err);
				}

				resolve();
			});
		});
	}
Leave a chat room group
@param {int} groupId
@param {function} [callback]
@returns {Promise}