code: func diffSubjectLists(list1 []rbacv1.Subject, list2 []rbacv1.Subject) (list1Only []rbacv1.Subject, list2Only []rbacv1.Subject) {
  	for _, list1Item := range list1 {
  		if !contains(list2, list1Item) {
  			if !contains(list1Only, list1Item) {
  				list1Only = append(list1Only, list1Item)
  			}
  		}
  	}
  	for _, list2Item := range list2 {
  		if !contains(list1, list2Item) {
  			if !contains(list2Only, list2Item) {
  				list2Only = append(list2Only, list2Item)
  			}
  		}
  	}
  	return
  }
docs: // diffSubjectLists returns lists containing the items unique to each provided list:
  //   list1Only = list1 - list2
  //   list2Only = list2 - list1
  // if both returned lists are empty, the provided lists are equal