SHOW_ELEMENT,
    {
      acceptNode: function (node) {
        if (previous === node.parentNode) {
          return NodeFilter.FILTER_REJECT;
        } else {
          previous = node;
        }
        if (node.nodeName === 'EMU-CLAUSE' || node.nodeName === 'EMU-INTRO' || node.nodeName === 'EMU-ANNEX') {
          return NodeFilter.FILTER_ACCEPT;
        } else {
          return NodeFilter.FILTER_SKIP;
        }
      }
    },
    false
    );

  return treeWalker;
}

Menu.prototype.toggle = function ()