getModel method
Gets the selection model. If the model is null, create one from
configuration and the processed seriesList
passed in.
Implementation
common.SelectionModel<D> getModel(
List<common.ImmutableSeries<D>> seriesList) {
_model ??= common.SelectionModel<D>.fromConfig(
selectedDataConfig, selectedSeriesConfig, seriesList);
return _model!;
}