code: function (root, expandStack, applyFishEyeViewToEachNode) {
      if (root._private.data.collapsedChildren != null) {
        expandStack.push(root);
        this.expandNode(root, applyFishEyeViewToEachNode);
      }
      var children = root.children();
      for (var i = 0; i < children.length; i++) {
        var node = children[i];
        this.expandAllTopDown(node, expandStack, applyFishEyeViewToEachNode);
      }
    }
docs: /*
  Expands the root and its collapsed descendents in top down order.