d3jstree图例展示出错，跪求大神指点

Question

<script src="http://d3js.org/d3.v3.min.js"></script>
<script>
  var diameter = 960;
  /*定义一个Tree对象,定义旋转角度和最大半径*/
  var tree = d3.layout.tree().size([360, diameter / 2 - 120]).separation(function(a, b) { return (a.parent == b.parent ? 1 : 2) / a.depth; });
  /*定义布局方向*/
  var diagonal = d3.svg.diagonal.radial().projection(function(d) { return [d.y, d.x / 180 * Math.PI]; });
  /*新建画布，移动到圆心位置*/
  var svg = d3.select("body").append("svg").attr("width", diameter).attr("height", diameter - 150).append("g").attr("transform", "translate(" + diameter / 2 + "," + diameter / 2 + ")");

  d3.json("test2.json", function(error, root) {
    if (error) throw error;
    /*根据数据生成nodes集合，获取node集合的关系集合*/
    var nodes = tree.nodes(root),
    links = tree.links(nodes);

    var link = svg.selectAll(".link").data(links).enter().append("path").attr("class", "link").attr("d", diagonal).style("stroke",function(d){
      if(d.type == 1){/*当前企业*/
        d.level = "#24a6da";
      }else if(d.type == 2){/*股东*/
        d.level = "#4cd1e0";
      }else if(d.type == 3){/*对外投资*/
        d.level = "#92db8c";
      }
      return d.level});

    var node = svg.selectAll(".node").data(nodes).enter().append("g").attr("class", "node").attr("transform", function(d) { return "rotate(" + (d.x - 90) + ")translate(" + d.y + ")"; })

    /*为节点添加圆形标记,如果有子节点为蓝色，否则白色*/
    node.append("circle").attr("r", 6.5).style("fill", function(d) { return d.level; });

/*图例的位置大小*/
var color_block = level_groups.data('links').append('rect').attr("x", diameter/2 - 60).attr("width",20).attr("height",20).attr("fill",function(d){
if(d.type == 1){/*当前企业*/
d.level = "#24a6da";return d.level
}else if(d.type == 2){/*股东*/
d.level = "#4cd1e0";return d.level
}else if(d.type == 3){/*对外投资*/
d.level = "#92db8c";return d.level
}});
var labelText = level_groups.append("text").attr('dx', diameter/2 - 80).attr("dy","18").attr("text-anchor", "end").text(function(d){ return d.type; }).style('stroke',"#000");/*文字末尾对齐，颜色#000*/
});

  d3.select(self.frameElement).style("height", diameter - 150 + "px");


</script>

    以下为json数据：
    {
"id": "736c799c-7765-4e02-ab83-b57d7716d7bb",
"name": "品尚电子商务有限公司",
"type": 1,
"level": "#09f",
"children": [{
    "id": "bfed1dd8-3228-4e36-9577-3d94ac16f8ab",
    "name": "民生电商控股（深圳）有限公司",
    "type": 2,
    "level": "#09f",
        }]

}

Answer 1

http://www.cleey.com/blog/single/id/705.html