@Override
    public void clear() {
      map.clear();
    }

    @Override
    Set<K> createKeySet() {
      return map.keySet();
    }

    @Override
    Collection<V> createValues() {
      return map.values();
    }

    @Override
    public Set<Entry<K, V>> entries() {
      return map.entrySet();
    }

    @Override

   * corresponding keys.
   */
  @Override
  public ImmutableCollection<V> values() {
    return valueList;
  }

  @Override
  ImmutableCollection<V> createValues() {
    throw new AssertionError("should never be called");
  }

  /**
   * Returns the comparator that orders the keys, which is {@link Ordering#natural()} when the