code: def _ensure_opened(self):
          
          if not self._opened:
              self._opened = True
              self._update_servers()
  
              # Start or restart the events publishing thread.
              if self._publish_tp or self._publish_server:
                  self.__events_executor.open()
  
          # Ensure that the monitors are open.
          for server in itervalues(self._servers):
              server.open()
docs: Start monitors, or restart after a fork.
  
          Hold the lock when calling this.