code: function() {
  
              var self = this;
  
              // Draw the chart,
              $('#' + self.getId('chart')).html('')
                .bilevelSunburst({date: self.options.date}, 
                                 self.treemapData);
          }
docs: create this utility function to draw chart,
  we could use it whenever we need.
  For example,
  after we re-arrange the dashboard, we will need re-draw the chart.
  the chart will re-calculate all positions.