map.put(entry.getKey(), entry.getValue());
    }
    return map;
  }

  static <T> Comparator<T> arbitraryNullFriendlyComparator() {
    return new NullFriendlyComparator<>();
  }

  private static final class NullFriendlyComparator<T> implements Comparator<T>, Serializable {
    @Override
    public int compare(T left, T right) {
      return String.valueOf(left).compareTo(String.valueOf(right));
    }