//    visible to done(). This is because there is no happens before edge between the write and a
  //    (hypothetical) unsafe read by our caller. Note: adding 'volatile' does not fix this issue,
  //    it would just add an edge such that if done() observed non-null, then it would also

   */
  @SuppressWarnings("unchecked") // can cast to <T> because non-Ts are removed
  @GwtIncompatible // Class.isInstance
  public static <T> UnmodifiableIterator<T> filter(Iterator<?> unfiltered, Class<T> desiredType) {
    return (UnmodifiableIterator<T>) filter(unfiltered, instanceOf(desiredType));
  }

  /**
   * Returns {@code true} if one or more elements returned by {@code iterator} satisfy the given
   * predicate.
   */

   */
  @SuppressWarnings("unchecked") // can cast to <T> because non-Ts are removed
  @GwtIncompatible // Class.isInstance
  public static <T> UnmodifiableIterator<T> filter(Iterator<?> unfiltered, Class<T> desiredType) {
    return (UnmodifiableIterator<T>) filter(unfiltered, instanceOf(desiredType));
  }

  /**
   * Returns {@code true} if one or more elements returned by {@code iterator} satisfy the given
   * predicate.
   */