code: function(nodes) {
        if (nodes.length == 0) return nodes;
        var results = [], n;
        for (var i = 0, l = nodes.length; i < l; i++)
          if (!(n = nodes[i])._counted) {
            n._counted = true;
            results.push(Element.extend(n));
          }
        return Selector.handlers.unmark(results);
      }
docs: filters out duplicates and extends all nodes