getDescendants method Null safety

Stream<SmoothCategory<T>> getDescendants()

This returns a depth-first iterable over the descendants of this node.

Implementation

Stream<SmoothCategory<T>> getDescendants() async* {
  await for (final SmoothCategory<T> child in getChildren()) {
    yield* child.getDescendants();
    yield child;
  }
}