@CollectionFeature.Require(SUPPORTS_ITERATOR_REMOVE)
  public void testKeysEntrySetIteratorRemove() {
    Multiset<K> keys = multimap().keys();
    Iterator<Multiset.Entry<K>> itr = keys.entrySet().iterator();
    assertEquals(Multisets.immutableEntry(k0(), 1), itr.next());
    itr.remove();
    assertTrue(multimap().isEmpty());
  }

  @CollectionSize.Require(SEVERAL)
  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testKeysEntrySetRemove() {

    }

    @Override
    public boolean removeAll(Collection<?> collection) {
      boolean changed = false;
      Iterator<E> itr = unfiltered.iterator();
      while (itr.hasNext()) {
        E e = itr.next();
        if (predicate.apply(e) && collection.contains(e)) {
          itr.remove();
          changed = true;
        }
      }
      return changed;
    }

    @Override

  @Override
  public Iterator<E> iterator() {
    Monitor monitor = this.monitor;
    monitor.enter();
    try {
      return new Itr();
    } finally {
      monitor.leave();
    }
  }

  /** Iterator for MonitorBasedArrayBlockingQueue */
  private class Itr implements Iterator<E> {
    /** Index of element to be returned by next, or a negative number if no such. */
    private int nextIndex;

    /**

    Multiset.Entry<E> entry = getOnlyElement(getMultiset().entrySet());
    assertEquals(3, entry.getCount());
    Iterator<E> itr = getMultiset().iterator();
    itr.next();
    itr.remove();
    assertEquals(2, entry.getCount());
    itr.next();
    itr.remove();
    itr.next();
    itr.remove();
    assertEquals(0, entry.getCount());
  }

  @CollectionSize.Require(SEVERAL)

    } else {
      return new Itr<E>(this, index);
    }
  }

  /** A singleton implementation of iterator() for the empty ImmutableList. */
  // TODO(b/345814817): Move this to RegularImmutableList?
  @SuppressWarnings("ClassInitializationDeadlock")
  private static final UnmodifiableListIterator<Object> EMPTY_ITR =
      new Itr<Object>(RegularImmutableList.EMPTY, 0);

    }

    @Override
    public boolean hasNext() {
      return !stack.isEmpty();
    }

    @Override
    public T next() {
      Iterator<T> itr = stack.getLast(); // throws NSEE if empty
      T result = checkNotNull(itr.next());
      if (!itr.hasNext()) {
        stack.removeLast();
      }
      Iterator<T> childItr = children(result).iterator();
      if (childItr.hasNext()) {

  @Override
  public Iterator<E> iterator() {
    Monitor monitor = this.monitor;
    monitor.enter();
    try {
      return new Itr();
    } finally {
      monitor.leave();
    }
  }

  /** Iterator for MonitorBasedArrayBlockingQueue */
  private class Itr implements Iterator<E> {
    /** Index of element to be returned by next, or a negative number if no such. */
    private int nextIndex;

    /**

   */
  int adjustAfterRemove(int indexBeforeRemove, @SuppressWarnings("unused") int indexRemoved) {
    return indexBeforeRemove - 1;
  }

  private abstract class Itr<T extends @Nullable Object> implements Iterator<T> {
    int expectedMetadata = metadata;
    int currentIndex = firstEntryIndex();
    int indexToRemove = -1;

    @Override
    public boolean hasNext() {

   */
  int adjustAfterRemove(int indexBeforeRemove, @SuppressWarnings("unused") int indexRemoved) {
    return indexBeforeRemove - 1;
  }

  private abstract class Itr<T extends @Nullable Object> implements Iterator<T> {
    int expectedMetadata = metadata;
    int currentIndex = firstEntryIndex();
    int indexToRemove = -1;

    @Override
    public boolean hasNext() {

      collection.clear();
      totalSize -= count;
    }
  }

  private abstract class Itr<T extends @Nullable Object> implements Iterator<T> {
    final Iterator<Entry<K, Collection<V>>> keyIterator;
    @Nullable K key;
    @Nullable Collection<V> collection;
    Iterator<V> valueIterator;

    Itr() {
      keyIterator = map.entrySet().iterator();
      key = null;
      collection = null;