}

    @Override
    public Collection<V> values() {
      return new Values<>(this);
    }

    @Override
    public String toString() {
      return standardToString();
    }
  }

  /** Returns a map from the ith element of list to i. */
  static <E> ImmutableMap<E, Integer> indexMap(Collection<E> list) {

    }

    @Override
    public Collection<V> values() {
      return new Values<>(this);
    }

    @Override
    public String toString() {
      return standardToString();
    }
  }

  /** Returns a map from the ith element of list to i. */
  static <E> ImmutableMap<E, Integer> indexMap(Collection<E> list) {