anchor.diff:          data: data[series]));
   
       return list;
  -  }
  -
  -  CategoryModel get model => super.model;
  -
  -  void set model(ChartModel model) {
  -    if (model is! CategoryModel)
  -      return;
  -
  -    super.model = model;
     }
   }
   
  
positive.code:       data[series] = values;
      }
  
      for (String series in data.keys)
        list.add(new ChartDataSets(
          name: series,
          color: model.getSeriesStyle(series, SeriesStyle.color),
          borderRadius: model.getSeriesStyle(series, SeriesStyle.borderRadius),
          fillOpacity: model.getSeriesStyle(series, SeriesStyle.fillOpacity),
  
negative.code:   static final String line = 'line';
  }
  
  abstract class Chart<S extends Comparable, C extends Comparable, T extends ChartModel<S, C>> {
  
    Element get element;
  
  