Multimap<String, Integer> filtered = filterValues(keyFiltered, VALUE_PREDICATE);
    assertEquals(1, filtered.size());
    assertTrue(filtered.containsEntry("foo", 1));
    assertTrue(filtered.keySet().retainAll(asList("cat", "dog")));
    assertEquals(0, filtered.size());
  }

  // TODO(jlevy): Many more tests needed.

  }

  /** An implementation of {@link Multiset#retainAll}. */
  static boolean retainAllImpl(Multiset<?> self, Collection<?> elementsToRetain) {
    checkNotNull(elementsToRetain);
    Collection<?> collection =
        (elementsToRetain instanceof Multiset)
            ? ((Multiset<?>) elementsToRetain).elementSet()
            : elementsToRetain;

    return self.elementSet().retainAll(collection);
  }

  }

  /** An implementation of {@link Multiset#retainAll}. */
  static boolean retainAllImpl(Multiset<?> self, Collection<?> elementsToRetain) {
    checkNotNull(elementsToRetain);
    Collection<?> collection =
        (elementsToRetain instanceof Multiset)
            ? ((Multiset<?>) elementsToRetain).elementSet()
            : elementsToRetain;

    return self.elementSet().retainAll(collection);
  }

      return standardRemove(object);
    }

    @Override
    public boolean removeAll(Collection<?> collection) {
      return standardRemoveAll(collection);
    }

    @Override
    public boolean retainAll(Collection<?> collection) {
      return standardRetainAll(collection);
    }

    @Override
    public Object[] toArray() {
      return standardToArray();
    }

    @Override

      return standardRemove(object);
    }

    @Override
    public boolean removeAll(Collection<?> collection) {
      return standardRemoveAll(collection);
    }

    @Override
    public boolean retainAll(Collection<?> collection) {
      return standardRetainAll(collection);
    }

    @Override
    public Object[] toArray() {
      return standardToArray();
    }

    @Override

        }

        public boolean removeAll(final Collection<?> c) {
            return parent.removeAll(c);
        }

        public boolean retainAll(final Collection<?> c) {
            return parent.retainAll(c);
        }

        public void clear() {
            parent.clear();
        }

        public boolean equals(final Object o) {
            return parent.equals(o);

    } catch (UnsupportedOperationException expected) {
    }
    assertCollectionsAreEquivalent(copy, collection);

    try {
      collection.retainAll(siblingCollection);
      fail("retainAll succeeded on unmodifiable collection");
    } catch (UnsupportedOperationException expected) {
    }
    assertCollectionsAreEquivalent(copy, collection);
  }

  /**

      return standardRemove(object);
    }

    @Override
    public boolean removeAll(Collection<?> collection) {
      return standardRemoveAll(collection);
    }

    @Override
    public boolean retainAll(Collection<?> collection) {
      return standardRetainAll(collection);
    }

    @Override
    public Object[] toArray() {
      return standardToArray();
    }

    @Override

      return standardRemove(object);
    }

    @Override
    public boolean removeAll(Collection<?> collection) {
      return standardRemoveAll(collection);
    }

    @Override
    public boolean retainAll(Collection<?> collection) {
      return standardRetainAll(collection);
    }

    @Override
    public Object[] toArray() {
      return standardToArray();
    }

    @Override

        Predicates.<Entry<K, V>>and(
            multimap.entryPredicate(), Maps.<V>valuePredicateOnEntries(Predicates.in(c))));
  }

  @Override
  public boolean retainAll(Collection<?> c) {
    return Iterables.removeIf(
        multimap.unfiltered().entries(),
        // explicit <Entry<K, V>> is required to build with JDK6
        Predicates.<Entry<K, V>>and(