code: @Override
      public void addSubInterfacesInfo(Content classInfoTree) {
          if (utils.isInterface(typeElement)) {
              Set<TypeElement> subInterfaces = classtree.allSubClasses(typeElement, false);
              if (!subInterfaces.isEmpty()) {
                  Content label = contents.subinterfacesLabel;
                  Content dt = HtmlTree.DT(label);
                  Content dl = HtmlTree.DL(dt);
                  dl.addContent(getClassLinks(LinkInfoImpl.Kind.SUBINTERFACES,
                          subInterfaces));
                  classInfoTree.addContent(dl);
              }
          }
      }
docs: {@inheritDoc}