code: func (cc *Controller) graduateAssignedToLastKnownGood() error {
  	// get assigned
  	assigned, err := cc.checkpointStore.Assigned()
  	if err != nil {
  		return err
  	}
  	// get last-known-good
  	lastKnownGood, err := cc.checkpointStore.LastKnownGood()
  	if err != nil {
  		return err
  	}
  	// if the sources are equal, no need to change
  	if assigned == lastKnownGood ||
  		assigned != nil && lastKnownGood != nil && apiequality.Semantic.DeepEqual(assigned.NodeConfigSource(), lastKnownGood.NodeConfigSource()) {
  		return nil
  	}
  	// update last-known-good
  	err = cc.checkpointStore.SetLastKnownGood(assigned)
  	if err != nil {
  		return err
  	}
  	// update the status to reflect the new last-known-good config
  	cc.configStatus.SetLastKnownGood(assigned.NodeConfigSource())
  	utillog.Infof("updated last-known-good config to %s, UID: %s, ResourceVersion: %s", assigned.APIPath(), assigned.UID(), assigned.ResourceVersion())
  	return nil
  }
docs: // graduateAssignedToLastKnownGood sets the last-known-good in the checkpointStore
  // to the same value as the assigned config maintained by the checkpointStore