selectIndex method
Implementation
void selectIndex(int dataIndex, {int seriesIndex = 0, dynamic value}) {
if (_disposed) return;
_selection = ChartSelection(
seriesIndex: seriesIndex,
dataIndex: dataIndex,
value: value,
).snapshot();
_emitSelection(_selection);
onDataPointTap?.call(seriesIndex, dataIndex, value);
_notifyIfAlive();
}