}
  }

  static class DummyValueReference<K, V> implements ValueReference<K, V> {
    private @Nullable V value;
    boolean loading = false;

    public DummyValueReference() {
      this.loading = true;
    }

    public DummyValueReference(V value) {
      this.value = value;
    }

    public static <K, V> DummyValueReference<K, V> create(V value) {