code: function encodeSummaryArticle(article, recursive) {
      var articles = undefined;
      if (recursive !== false) {
          articles = article.getArticles()
              .map(encodeSummaryArticle)
              .toJS();
      }
  
      return {
          title: article.getTitle(),
          level: article.getLevel(),
          depth: article.getDepth(),
          anchor: article.getAnchor(),
          url: article.getUrl(),
          path: article.getPath(),
          ref: article.getRef(),
          articles: articles
      };
  }
docs: Encode a SummaryArticle to JSON
  
  @param {SummaryArticle}
  @return {Object}