code: @Override
      @JsonIgnore
      public Set<String> getPossibleUserAttributeNames(final IPersonAttributeDaoFilter filter) {
          final Set<String> rslt = new LinkedHashSet<>();
  
          for (final AttributeRule rule : this.rules) {
              final Set<String> possibleUserAttributeNames = rule.getPossibleUserAttributeNames();
              rslt.addAll(possibleUserAttributeNames);
          }
  
          return rslt;
      }
docs: Aggregates the results of calling {@link AttributeRule#getPossibleUserAttributeNames()}
  on each {@link AttributeRule} instance in the rules array.
  
  @see IPersonAttributeDao#getPossibleUserAttributeNames(org.apereo.services.persondir.IPersonAttributeDaoFilter)