docs: public List<SpecNode> getAllSpecNodes() {
          final ArrayList<SpecNode> retValue = new ArrayList<SpecNode>();
  
          // Add all the levels
          retValue.addAll(levels);
  
          // Add all the topics
          for (final Entry<Integer, List<ITopicNode>> topicEntry : topics.entrySet()) {
              for (final ITopicNode topic : topicEntry.getValue()) {
                  if (topic instanceof SpecNode) {
                      retValue.add((SpecNode) topic);
                  }
              }
          }
  
          return retValue;
      }