changeValue method
Implementation
@override
void changeValue(LineStyle begin, LineStyle end) {
super.changeValue(begin, end);
if (begin.shadow != null && end.shadow != null) {
_shadowTween = BoxShadowTween(begin.shadow!, end.shadow!);
}
if (begin.shader != null && end.shader != null) {
_shaderTween = ChartShaderTween(begin.shader!, end.shader!);
}
}