@Override
  public PackageSet map(@NotNull Function<? super PackageSet, ? extends PackageSet> transformation) {
    PackageSet updated = transformation.apply(myComplementarySet);
    return updated != myComplementarySet ? new ComplementPackageSet(updated) : this;
  }
@Override
  public PackageSet map(@NotNull Function<? super PackageSet, ? extends PackageSet> transformation)