setData method
Implementation
@override
void setData(int index, ChartSegment segment) {
  super.setData(index, segment);
  segment as StackedAreaSegment<T, D>
    ..series = this
    ..currentSegmentIndex = 0
    .._xValues = xValues
    .._topValues = topValues
    .._bottomValues = bottomValues
    .._bottom = xAxis!.crossesAt;
}