reviseSetItems method
Adds all the items, replacing items that already exist, preserving other items.
Implementation
TSubclass reviseSetItems(Iterable<TModel> newItems) {
final revised = Map<String, TModel>.from(items);
for(final item in newItems) {
final id = itemId(item);
revised[id] = item;
}
return reviseItems(revised);
}