{
  "widgettype": "ChartHeatmap",
  "options": {
    "data": {
      "x_labels": ["A", "B", "C"],
      "y_labels": ["1", "2", "3"], 
      "values": [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
    },
    "width": "400px",
    "height": "300px"
  }
}