code: public void buildInterfaceSummary(XMLNode node, Content summaryContentTree) {
          String interfaceTableSummary =
                  configuration.getText("doclet.Member_Table_Summary",
                  configuration.getText("doclet.Interface_Summary"),
                  configuration.getText("doclet.interfaces"));
          List<String> interfaceTableHeader = Arrays.asList(configuration.getText("doclet.Interface"),
          configuration.getText("doclet.Description"));
  
          SortedSet<TypeElement> ilist = utils.isSpecified(packageElement)
                          ? utils.getTypeElementsAsSortedSet(utils.getInterfaces(packageElement))
                          : configuration.typeElementCatalog.interfaces(packageElement);
          SortedSet<TypeElement> interfaces = utils.filterOutPrivateClasses(ilist, configuration.javafx);
          if (!interfaces.isEmpty()) {
              packageWriter.addClassesSummary(interfaces,
                      configuration.getText("doclet.Interface_Summary"),
                      interfaceTableSummary, interfaceTableHeader, summaryContentTree);
          }
      }
docs: Build the summary for the interfaces in this package.
  
  @param node the XML element that specifies which components to document
  @param summaryContentTree the summary tree to which the interface summary
  will be added