* while writing to it in another. All it does is help with _reading_ from multiple threads
   * concurrently. For more information, see AbstractNetworkTest.concurrentIteration.
   */
  @CheckForNull private transient volatile Entry<K, V> cacheEntry;

  MapIteratorCache(Map<K, V> backingMap) {
    this.backingMap = checkNotNull(backingMap);
  }

  @CanIgnoreReturnValue