docs: @Override
      public Document toDocument() {
          // if (project == null) throw new NullPointerException("No project");
          assert project != null;
  
          DocumentFactory docFactory = new DocumentFactory();
          Document document = docFactory.createDocument();
          Dom4JXMLOutput treeBuilder = new Dom4JXMLOutput(document);
  
          try {
              writeXML(treeBuilder);
          } catch (IOException e) {
              // Can't happen
          }
          return document;
      }