*/
  @CanIgnoreReturnValue // pushed down from class to method
  @Override
  public boolean add(E e) {
    return offer(e);
  }

  /**
   * Inserts the specified element into this priority queue.
   *
   * @param e the element to add
   * @return {@code true} (as specified by {@link Queue#offer})
   * @throws ClassCastException if the specified element cannot be compared with elements currently

 * to the methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change
 * the behaviour of {@link #offer} which can lead to unexpected behaviour. In this case, you should
 * override {@code offer} as well, either providing your own implementation, or delegating to the
 * provided {@code standardOffer} method.
 *

		// free-version to track it for asynchronous
		// deletion via scanner.
		ver, err := x.getIdx(i)
		if err != nil {
			return err
		}

		if freeVersion, toFree := ver.ObjectV2.InitFreeVersion(fi); toFree {
			return x.addVersion(freeVersion)
		}
		return nil
	}
	return nil

    private final Deque<E> delegate = Lists.newLinkedList();
    public final Object mutex = new Integer(1); // something Serializable

    @Override
    public boolean offer(E o) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.offer(o);
    }

    @Override
    public @Nullable E poll() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.poll();
    }

    @Override

   */
  @CanIgnoreReturnValue // pushed down from class to method
  @Override
  public boolean add(E e) {
    return offer(e);
  }

  /**
   * Inserts the specified element into this priority queue.
   *
   * @param e the element to add
   * @return {@code true} (as specified by {@link Queue#offer})
   * @throws ClassCastException if the specified element cannot be compared with elements currently

 * methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change the
 * behavior of {@link #offer} which can lead to unexpected behavior. In this case, you should
 * override {@code offer} as well.
 *
 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code

    written offer to provide the Corresponding Source.  This
    alternative is allowed only occasionally and noncommercially, and
    only if you received the object code with such an offer, in accord
    with subsection 6b.

    d) Convey the object code by offering access from a designated
    place (gratis or for a charge), and offer equivalent access to the

  private static final class TestQueue<E> implements Queue<E> {
    private final Queue<E> delegate = Lists.newLinkedList();
    public Object mutex;

    @Override
    public boolean offer(E o) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.offer(o);
    }

    @Override
    public @Nullable E poll() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.poll();
    }

    @Override

  }

  // BlockingQueue.take() tests
  public void testTakeWithNoWait() {
    Stopwatch stopwatch = Stopwatch.createStarted();
    BlockingQueue<String> queue = new ArrayBlockingQueue<>(1);
    assertTrue(queue.offer(""));
    assertEquals("", takeUninterruptibly(queue));
    assertTimeNotPassed(stopwatch, LONG_DELAY_MS);
  }

  public void testTakeNoInterrupt() {
    TimedTakeQueue queue = TimedTakeQueue.createWithDelay(20);

       5. Downstream recipients.

            a. Offer from the Licensor -- Licensed Material. Every
               recipient of the Licensed Material automatically
               receives an offer from the Licensor to exercise the
               Licensed Rights under the terms and conditions of this
               Public License.

            b. No downstream restrictions. You may not offer or impose