code: public static void exportRocChartsToHtmlFile(ROCMultiClass roc, File file) throws Exception {
          String rocAsHtml = rocChartToHtml(roc);
          FileUtils.writeStringToFile(file, rocAsHtml, StandardCharsets.UTF_8);
      }
docs: Given a {@link ROCMultiClass} chart, export the ROC chart and precision vs. recall charts to a stand-alone HTML file
  @param roc  ROC to export
  @param file File to export to