How to use the attrs.Attrs.HeartBeat function in attrs

import Adafruit_BluefruitLE
from Adafruit_BluefruitLE.services import UART as OriginalUART
import Queue
import uuid
import time
from attrs import Attrs
import logging
log = logging.getLogger(__name__)

class ShareUART (OriginalUART):
  ADVERTISED = [Attrs.CradleService]
  # SERVICES = [Attrs.DeviceService]
  SERVICES = [Attrs.CradleService]
  CHARACTERISTICS = [Attrs.AuthenticationCode, Attrs.Command, Attrs.Response, Attrs.ShareMessageReceiver, Attrs.ShareMessageResponse, Attrs.HeartBeat, Attrs.DeviceService, Attrs.PowerLevel]

  UART_SERVICE_UUID = Attrs.CradleService
  TX_CHAR_UUID = Attrs.Command
  RX_CHAR_UUID = Attrs.Response
  pass
class Share2UART (OriginalUART):
  # ADVERTISED = [Attrs.CradleService2]
  # ADVERTISED = [Attrs.VENDOR_UUID]
  ADVERTISED = [Attrs.VENDOR_UUID]
  # SERVICES = [Attrs.DeviceService]
  # SERVICES = [Attrs.CradleService2, Attrs.VENDOR_UUID]
  SERVICES = [Attrs.VENDOR_UUID, Attrs.DeviceService]
  # CHARACTERISTICS = [Attrs.AuthenticationCode2, Attrs.Command2, Attrs.Response2, Attrs.ShareMessageReceiver2, Attrs.ShareMessageResponse2, Attrs.HeartBeat2, Attrs.DeviceService, Attrs.PowerLevel]
  CHARACTERISTICS = [ ]

  HEARTBEAT_UUID = Attrs.HeartBeat2