code: function() {
      this.jsonInit({
        "id": "event_whenbroadcastreceived",
        "message0": Blockly.Msg.EVENT_WHENBROADCASTRECEIVED,
        "args0": [
          {
            "type": "field_variable",
            "name": "BROADCAST_OPTION",
            "variableTypes": [Blockly.BROADCAST_MESSAGE_VARIABLE_TYPE],
            "variable": Blockly.Msg.DEFAULT_BROADCAST_MESSAGE_NAME
          }
        ],
        "category": Blockly.Categories.event,
        "extensions": ["colours_event", "shape_hat"]
      });
    }
docs: Block for when broadcast received.
  @this Blockly.Block