How to use the @jupyterlab/codemirror.CodeMirrorEditor.DEFAULT_THEME function in @jupyterlab/codemirror

function initializeMarked(): void {
    if (initialized) {
      return;
    }
    initialized = true;
    marked.setOptions({
      gfm: true,
      sanitize: false,
      tables: true,
      // breaks: true; We can't use GFM breaks as it causes problems with tables
      langPrefix: `cm-s-${CodeMirrorEditor.DEFAULT_THEME} language-`,
      highlight: (code, lang, callback) => {
        if (!lang) {
            // no language, no highlight
            if (callback) {
                callback(null, code);
                return;
            } else {
                return code;
            }
        }
        Mode.ensure(lang).then(spec => {
          let el = document.createElement('div');
          if (!spec) {
              console.log(`No CodeMirror mode: ${lang}`);
              callback(null, code);
              return;