code: def start(self):
          
          def _heartbeat():
              if not self._client.lifecycle.is_live:
                  return
              self._heartbeat()
              self._heartbeat_timer = self._client.reactor.add_timer(self._heartbeat_interval, _heartbeat)
  
          self._heartbeat_timer = self._client.reactor.add_timer(self._heartbeat_interval, _heartbeat)
docs: Starts sending periodic HeartBeat operations.