/** Returns whether {@code obj} is <b>not</b> an instance of {@code DelegatingToFuture}. */
  // This method lets us:
  // - avoid exposing DelegatingToFuture to the whole package
  // - avoid fighting with the relative operator precedence of `instanceof` and `!`
  static boolean notInstanceOfDelegatingToFuture(@Nullable Object obj) {
    return !(obj instanceof DelegatingToFuture);
  }

  @Override
  public boolean isDone() {

  // * Be responsive to interruption
  // * Don't create Waiter nodes if you aren't going to park, this helps reduce contention on
  //   waitersField.
  // * Future completion is defined by when #valueField becomes non-null/non DelegatingToFuture
  // * Future completion can be observed if the waitersField field contains a TOMBSTONE

  // Timed Get
  // There are a few design constraints to consider