code: func printDiff(oldResources, newResources map[schema.GroupVersionResource]struct{}) string {
  	removed := sets.NewString()
  	for oldResource := range oldResources {
  		if _, ok := newResources[oldResource]; !ok {
  			removed.Insert(fmt.Sprintf("%+v", oldResource))
  		}
  	}
  	added := sets.NewString()
  	for newResource := range newResources {
  		if _, ok := oldResources[newResource]; !ok {
  			added.Insert(fmt.Sprintf("%+v", newResource))
  		}
  	}
  	return fmt.Sprintf("added: %v, removed: %v", added.List(), removed.List())
  }
docs: // printDiff returns a human-readable summary of what resources were added and removed