static Set<RefPackage> calculateTransitiveDependentsForPackage(
    RefPackage refPackage) {
    final Set<RefPackage> dependents =
      refPackage.getUserData(TRANSITIVE_DEPENDENT_PACKAGES_KEY);
    if (dependents != null) {
      return dependents;
    }
    final Set<RefPackage> newDependents = new HashSet<>();
    tabulateTransitiveDependentPackages(refPackage, newDependents);
    refPackage.putUserData(TRANSITIVE_DEPENDENT_PACKAGES_KEY, newDependents);
    return newDependents;
  }
static Set<RefPackage> calculateTransitiveDependentsForPackage(
    RefPackage refPackage)