private static @Nullable Configurable.Promo asPromo(Configurable c) {
    if (c instanceof Configurable.Promo) return (Configurable.Promo)c;

    if (c instanceof ConfigurableWrapper w && w.getConfigurable() instanceof Configurable.Promo) {
      return (Configurable.Promo)w.getConfigurable();
    }

    return null;
  }
private static @Nullable Configurable.Promo asPromo(Configurable c)