apply method
Applies this operation to the current list.
Modifies current in place and returns the effective operation
(e.g. populated with captured state like removed index).
Implementation
@override
OverlayOp apply(List<InteractiveOverlayImage> list) {
final res = list.removeAtKey(key);
if (!res.removed || res.overlay == null) return this;
return copyWith(index: res.index, removed: res.overlay);
}