def _wipe_expired(self):
        current_time = datetime.utcfromtimestamp(self._clock.seconds())
        evolver = self._information_wipers.evolver()
        for key, wipe in self._information_wipers.items():
            last_activity = wipe.last_activity()
            if current_time - last_activity >= EXPIRATION_TIME:
                self._deployment_state = wipe.update_cluster_state(
                    self._deployment_state
                )
                evolver.remove(key)
        self._information_wipers = evolver.persistent()
Clear any expired state from memory.
dataset/ETHPy150Open ClusterHQ/flocker/flocker/control/_clusterstate.py/ClusterStateService._wipe_expired