code: function querySelectorAll(sel, flag) {
        var nodes = this.root.querySelectorAll(normalize(sel));
        return !flag ? nodes : Array.prototype.map.call(nodes, function (node) {
          return node._tag || undefined;
        });
      }
docs: Gets Nodes or Tags by CSS selector
  @param { string } sel - CSS selector
  @param { boolean } flag - true for Tag