Removes each element of elements from this set.
void removeAll(Iterable<Object> elements) {
  for (Object element in elements) {
    if (_validKey(element)) _remove(element);
  }
}
    © 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
    https://api.dart.dev/stable/2.5.0/dart-collection/SplayTreeSet/removeAll.html