// covariantly (and cannot be subclassed to add non-covariant uses).
      @SuppressWarnings("unchecked")
      PeekingImpl<T> peeking = (PeekingImpl<T>) iterator;
      return peeking;
    }
    return new PeekingImpl<>(iterator);
  }

  /**
   * Simply returns its argument.
   *
   * @deprecated no need to use this
   * @since 10.0
   */

              // timed out?
              remainingNanos = endNanos - System.nanoTime();
              if (remainingNanos < SPIN_THRESHOLD_NANOS) {
                // Remove the waiter, one way or another we are done parking this thread.
                removeWaiter(node);
                break long_wait_loop; // jump down to the busy wait loop
              }
            }
          }
          oldHead = waiters; // re-read and loop.

   * reconstructed using public factory methods. This ensures that the implementation types remain
   * as implementation details.
   *
   * <p>Since the bimap is immutable, ImmutableBiMap doesn't require special logic for keeping the
   * bimap and its inverse in sync during serialization, the way AbstractBiMap does.
   */
  @J2ktIncompatible // serialization
  private static class SerializedForm<K, V> extends ImmutableMap.SerializedForm<K, V> {