ments": [
      {
        "data": { "id": "a" }},
      {
        "data": { "id": "b" }},
      {
        "data": { "id": "ab", "source": "a", "target": "b" }}],

    "style": [
      {
        "selector": "node",
        "style": {
          "background-color": "#666",
          "label": "data(id)"}
      },

      {
        "selector": "edge",
        "style": {
          "width": 3,
          "line-color": "#ccc",
          "target-arrow-color": "#ccc",
          "target-arrow-shape": "triangle",
       