* will throw an exception if there are duplicate keys. The {@code build()} method will soon be
     * deprecated.
     *
     * @throws IllegalArgumentException if any two keys are equal according to the comparator (which
     *     might be the keys' natural order)
     */
    @Override
    public ImmutableSortedMap<K, V> build() {
      return buildOrThrow();
    }

    /**

     * will throw an exception if there are duplicate keys. The {@code build()} method will soon be
     * deprecated.
     *
     * @throws IllegalArgumentException if any two keys are equal according to the comparator (which
     *     might be the keys' natural order)
     */
    @Override
    public ImmutableSortedMap<K, V> build() {
      return buildOrThrow();
    }

    /**

  }

  public static <K extends Comparable<? super K>, V> ImmutableSortedMap<K, V> of(K k1, V v1) {
    return copyOf(singletonMap(k1, v1));
  }

  public static <K extends Comparable<? super K>, V> ImmutableSortedMap<K, V> of(
      K k1, V v1, K k2, V v2) {
    return new Builder<K, V>(Ordering.natural()).put(k1, v1).put(k2, v2).build();
  }