}
protected abstract byte getChartType();
public DJChart build() throws ChartBuilderException {
if (chart.getDataset().getColumnsGroup() == null) throw new ChartBuilderException("The group to wich the chart is related must be specified");
if (chart.getDataset().getColumns().isEmpty()) throw new ChartBuilderException("At least one column to wich the chart is related must be specified");
return chart;
}