docs: private static <K, V> Collection<Entry<K, V>> constrainedEntries(
        Collection<Entry<K, V>> entries, MapConstraint<? super K, ? super V> constraint) {
      if (entries instanceof Set) {
        return constrainedEntrySet((Set<Entry<K, V>>) entries, constraint);
      }
      return new ConstrainedEntries<K, V>(entries, constraint);
    }