code: public void appendSpecTopic(final SpecTopic specTopic) {
          topics.add(specTopic);
          nodes.add(specTopic);
          if (specTopic.getParent() != null && specTopic.getParent() instanceof Level) {
              ((Level) specTopic.getParent()).removeSpecTopic(specTopic);
          }
          specTopic.setParent(this);
      }
docs: Adds a Content Specification Topic to the Level. If the Topic already has a parent, then it is removed from that parent
  and added to this level.
  
  @param specTopic The Content Specification Topic to be added to the level.