_index
        };

        // Create this node's content;
        let li = document.createElement('li');
        let button = this._makeButton(data.tag, data.id, data.index);
        li.appendChild(button);
        ul.appendChild(li);

        this._index++;
        let nodes = [data];

        // If this node has children...
        for (let i = 0; i < parent.children.length; i++) {
          let child = parent.children[i];
          // Skip <style> nodes;
          if (child.localName === 'style') {
     