}

  @Override
  public Collection<V> removeAll(@Nullable Object key) {
    return containsKey(key) ? unfiltered.removeAll(key) : unmodifiableEmptyCollection();
  }

  @SuppressWarnings("EmptyList") // ImmutableList doesn't support nullable element types
  Collection<V> unmodifiableEmptyCollection() {
    if (unfiltered instanceof SetMultimap) {
      return emptySet();
    } else {
      return emptyList();
    }
  }

  }

  @Override
  public Collection<V> removeAll(@Nullable Object key) {
    return containsKey(key) ? unfiltered.removeAll(key) : unmodifiableEmptyCollection();
  }

  @SuppressWarnings("EmptyList") // ImmutableList doesn't support nullable element types
  Collection<V> unmodifiableEmptyCollection() {
    if (unfiltered instanceof SetMultimap) {
      return emptySet();
    } else {
      return emptyList();
    }
  }