private @NotNull PersistentList<T> collectAllForLanguage(@NotNull Language language) {
    PersistentList<T> result = persistentListOf();
    for (Language l = language; l != null; l = l.getBaseLanguage()) {
      result = result.addAll(forKey(l));
    }
    return result;
  }
private @NotNull PersistentList<T> collectAllForLanguage(@NotNull Language language)