return copyToSet(asList(elements));
  }

  // Would use Maps.immutableEntry
  public static <K extends @Nullable Object, V extends @Nullable Object> Entry<K, V> mapEntry(
      K key, V value) {
    return singletonMap(key, value).entrySet().iterator().next();
  }

  private static boolean isEmpty(Iterable<?> iterable) {
    return iterable instanceof Collection