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
   * natural ordering of the keys is used. Note that its behavior is not consistent with {@link
   * TreeMap#comparator()}, which returns {@code null} to indicate natural ordering.

    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
   * natural ordering of the keys is used. Note that its behavior is not consistent with {@link
   * TreeMap#comparator()}, which returns {@code null} to indicate natural ordering.