code: public Set<String> getActiveCategorySet() {
          Set<String> result = new TreeSet<>();
          result.addAll(this.activeBugCategorySet);
          return result;
      }
docs: Return set of active (enabled) bug categories.
  
  Note that bug categories that are not explicity hidden will appear active
  even if they are not members of this set.
  
  @return the set of active categories