class ExternalIdBundle implements ImmutableBean, Iterable<ExternalId>,
    Serializable, Comparable<ExternalIdBundle>, ExternalBundleIdentifiable, ExternalIdOrBundle {

  public static ExternalIdBundle parse(final Iterable<String> strs) {
    ArgumentChecker.noNulls(strs, "strs");
    final List<ExternalId> externalIds = new ArrayList<ExternalId>();
    for (final String str : strs) {
      externalIds.add(ExternalId.parse(str));
    }
    return create(externalIds);
  }

  private  ExternalIdBundle();
  private  ExternalIdBundle(final ImmutableSortedSet<ExternalId> identifiers);
  private  ExternalIdBundle(
      SortedSet<ExternalId> externalIds);

}