sortedValues[index] = requireNonNull(values[i]);
          }
          return new ImmutableSortedMap<K, V>(
              new RegularImmutableSortedSet<K>(
                  ImmutableList.<K>asImmutableList(sortedKeys), comparator),
              ImmutableList.<V>asImmutableList(sortedValues));
      }
    }

    /**