) {
      elem.querySelectorAll(tocLevels).forEach(function (element) {
        notAllowedTitleIds = Array.isArray(notAllowedTitleIds) ?
          notAllowedTitleIds.concat(element.getAttribute('id')) :
          [element.getAttribute('id')];
      });
    }) : null;

    // expand
    expandContents ? expandContents.forEach(function(elem) {
      elem.querySelectorAll(tocLevels).forEach(function (element) {
        notAllowedTitleIds = Array.isArray(notAllowedTitleIds) ?
          notAllowedTitleIds.concat