customizeSegment method
Changes the series color, border color, and border width.
Implementation
@override
void customizeSegment(ChartSegment segment) {
final AreaSegment<T, D> areaSegment = segment as AreaSegment<T, D>;
updateSegmentColor(areaSegment, borderColor, borderWidth);
updateSegmentGradient(areaSegment,
gradientBounds: areaSegment._fillPath.getBounds(),
gradient: gradient,
borderGradient: borderGradient);
}