code: def _init_health_checker(self):
          
          stub = Health_pb2_grpc.HealthStub(channel=self._channel)
          self._health_check = stub.Check
          health_check_thread = threading.Thread(target=self._health_check_thread)
          health_check_thread.daemon = True
          health_check_thread.start()
docs: start the health checker stub and start a thread to ping it every 30 seconds
          :return: None