In Dart how to get the ID of clicked SVG object?

In Dart how to get the ID of clicked SVG object?

For the Dart code below:
for(var SVG_Element in SVG_Element_list){
SVG_Element.onClick.listen((event){
//some code
});
}
How to determine the ID of the clicked object? I tried "event.target.id"
and would only get the type of the Element like "line" or "circle".
How to get the ID?
Thanks!