@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)

  @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)

    }
  }

  @Override
  final Iterator<E> elementIterator() {
    return new Itr<E>() {
      @Override
      @ParametricNullness
      E result(int entryIndex) {
        return backingMap.getKey(entryIndex);
      }
    };
  }

  @Override
  final Iterator<Entry<E>> entryIterator() {
    return new Itr<Entry<E>>() {
      @Override
      Entry<E> result(int entryIndex) {

 * serialization of funnels. When possible, it is recommended that funnels be implemented as a
 * single-element enum to maintain serialization guarantees. See Effective Java (2nd Edition), Item
 * 3: "Enforce the singleton property with a private constructor or an enum type". For example:
 *
 * <pre>{@code
 * public enum PersonFunnel implements Funnel<Person> {
 *   INSTANCE;

    }
    List<?> list = (List<?>) o;
    if (list.size() != axes.size()) {
      return -1;
    }
    ListIterator<?> itr = list.listIterator();
    int computedIndex = 0;
    while (itr.hasNext()) {
      int axisIndex = itr.nextIndex();
      int elemIndex = axes.get(axisIndex).indexOf(itr.next());
      if (elemIndex == -1) {
        return -1;
      }
      computedIndex += elemIndex * axesSizeProduct[axisIndex + 1];

    Item<T> itemInfo = getItem(groupNumber, itemNumber);
    Item<T> relatedInfo = getItem(groupNumber, relatedItemNumber);

    T item = itemInfo.value;
    T related = relatedInfo.value;
    assertWithTemplate(
        "$ITEM must be $RELATIONSHIP to $OTHER",
        itemInfo,
        relatedInfo,
        equivalence.equivalent(item, related));

  private void testItems() {
    for (Object item : Iterables.concat(equalityGroups)) {
      assertTrue(item + " must not be Object#equals to null", !item.equals(null));
      assertTrue(
          item + " must not be Object#equals to an arbitrary object of another class",
          !item.equals(NotAnInstance.EQUAL_TO_NOTHING));
      assertTrue(item + " must be Object#equals to itself", item.equals(item));
      assertEquals(

      assertEquals(
          "the hash of " + item + " must be consistent",
          equivalence.hash(item),
          equivalence.hash(item));
    }
  }

      toRemove = -1;
    }
  }

  @Override
  Iterator<E> elementIterator() {
    return new Itr<E>() {
      @Override
      E output(int index) {
        return enumConstants[index];
      }
    };
  }

  @Override
  Iterator<Entry<E>> entryIterator() {
    return new Itr<Entry<E>>() {
      @Override
      Entry<E> output(final int index) {

        }
        if (elements.length > 1) {
          /*
           * When a test requests a multiset with duplicates, our plan of
           * "add an extra item 0 to A and an extra item 1 to B" really means
           * "add an extra item 0 to A and B," which isn't what we want.
           */
          if (!Objects.equal(elements[0], elements[1])) {
            multiset2.add(elements[1], 2);
          }
        }