private static Set<RefPackage> calculateDependentsForPackage(
    RefPackage refPackage) {
    final Set<RefPackage> dependents =
      refPackage.getUserData(DEPENDENT_PACKAGES_KEY);
    if (dependents != null) {
      return dependents;
    }
    final Set<RefPackage> newDependents = new HashSet<>();
    tabulateDependentPackages(refPackage, newDependents);
    newDependents.remove(refPackage);
    refPackage.putUserData(DEPENDENT_PACKAGES_KEY, newDependents);
    return newDependents;
  }
private static Set<RefPackage> calculateDependentsForPackage(
    RefPackage refPackage)