code: function buildChart() {
        var self = this;
  
        // If dataTable isn't set, build it
        var dataTable = _.isEmpty(self.dataTable) ? self.buildDataTable() : self.dataTable;
  
        self.wrapper = self.buildWrapper(self.chartType, dataTable, self.options, self.chartId);
  
        // Set the datatable on this instance
        self.dataTable = self.wrapper.getDataTable();
  
        // After chart is built, set it on this instance and resolve the promise.
        google.visualization.events.addOneTimeListener(self.wrapper, 'ready', function () {
          self.chart = self.wrapper.getChart();
          chartDeferred.resolve();
        });
      }
docs: Build the chart.
  
  @return void