docs: public Set<String> getIdAttributes(final BuildData buildData) {
          final Set<String> ids = new HashSet<String>();
  
          // Add all the level id attributes
          for (final Level level : levels) {
              ids.add(level.getUniqueLinkId(buildData.isUseFixedUrls()));
          }
  
          // Add all the topic id attributes
          for (final Entry<Integer, List<ITopicNode>> topicEntry : topics.entrySet()) {
              final List<ITopicNode> topics = topicEntry.getValue();
              for (final ITopicNode topic : topics) {
                  if (topic instanceof SpecTopic) {
                      final SpecTopic specTopic = (SpecTopic) topic;
                      ids.add(specTopic.getUniqueLinkId(buildData.isUseFixedUrls()));
                  }
              }
          }
  
          return ids;
      }