docs: def _callUpgradeAgent(self, ev_data, failTimeout) -> None:
          """
          Callback which is called when upgrade time come.
          Writes upgrade record to upgrade log and asks
          node control service to perform upgrade
  
          :param when: upgrade time
          :param version: version to upgrade to
          """
  
          logger.info("{}'s upgrader calling agent for upgrade".format(self))
          self._actionLog.append_started(ev_data)
          self._action_start_callback()
          self.scheduledAction = None
          asyncio.ensure_future(
              self._sendUpgradeRequest(ev_data, failTimeout))