addItem method
Implementation
@override
PresentationModel addItem(
PresentationModel model, BodyComponentModel newItem) {
List<BodyComponentModel> newItems = model.bodyComponents == null
? []
: model.bodyComponents!.map((e) => e).toList();
newItems.add(newItem);
var newModel = model.copyWith(bodyComponents: newItems);
return newModel;
}