How to use the @argdown/core.ClosedGroupPlugin function in @argdown/core

argdown.addPlugin(modelPlugin, "build-model");
const regroupPlugin = new RegroupPlugin();
argdown.addPlugin(regroupPlugin, "build-model");

const preselectionPlugin = new PreselectionPlugin();
argdown.addPlugin(preselectionPlugin, "build-map");
const statementSelectionPlugin = new StatementSelectionPlugin();
argdown.addPlugin(statementSelectionPlugin, "build-map");
const argumentSelectionPlugin = new ArgumentSelectionPlugin();
argdown.addPlugin(argumentSelectionPlugin, "build-map");
const mapPlugin = new MapPlugin();
argdown.addPlugin(mapPlugin, "build-map");
const groupPlugin = new GroupPlugin();
argdown.addPlugin(groupPlugin, "build-map");
const colorPlugin = new ColorPlugin();
argdown.addPlugin(new ClosedGroupPlugin(), "transform-closed-groups");
argdown.addPlugin(colorPlugin, "colorize");

const stdoutArgdown = new StdOutPlugin({
  dataKey: "input",
  isRequestData: true
});
argdown.addPlugin(stdoutArgdown, "stdout-argdown");
const saveAsArgdown = new SaveAsFilePlugin({
  outputDir: "./compiled",
  dataKey: "input",
  extension: ".argdown",
  isRequestData: true
});
argdown.addPlugin(saveAsArgdown, "save-as-argdown");

const htmlExport = new HtmlExportPlugin();

const groupPlugin = new GroupPlugin();
const dotExport = new DotExportPlugin();
const graphMLExport = new GraphMLExportPlugin();
import primer from "!!raw-loader!../public/examples/argdown-primer.argdown";

app.addPlugin(parserPlugin, "parse-input");
app.addPlugin(dataPlugin, "build-model");
app.addPlugin(modelPlugin, "build-model");
app.addPlugin(regroupPlugin, "build-model");
app.addPlugin(colorPlugin, "colorize");
app.addPlugin(preselectionPlugin, "build-map");
app.addPlugin(statementSelectionPlugin, "build-map");
app.addPlugin(argumentSelectionPlugin, "build-map");
app.addPlugin(mapPlugin, "build-map");
app.addPlugin(groupPlugin, "build-map");
app.addPlugin(new ClosedGroupPlugin(), "transform-closed-groups");
app.addPlugin(htmlExport, "export-html");
app.addPlugin(dotExport, "export-dot");
app.addPlugin(graphMLExport, "export-graphml");
app.addPlugin(jsonExport, "export-json");

Vue.use(Vuex);

var examples = {
  "argdown-primer": {
    id: "argdown-primer",
    title: "Argdown Primer",
    url: "/sandbox/examples/argdown-primer.argdown",
    cachedContent: primer
  },
  greenspan: {
    id: "greenspan",