ChartData
final T domain; // @required
final num? measure;
final T? domainLowerBound;
final num? measureLowerBound;
final T? domainUpperBound;
final num? measureUpperBound;
/// custom object you designed
final Object? others;
Inherit Class
class NumericData extends ChartData<num>
class OrdinalData extends ChartData<String>
class TimeData extends ChartData<DateTime>