code: public static <K, V> Builder<K, V> orderedBy(Comparator<K> comparator) {
      return new Builder<>(comparator);
    }
docs: Returns a builder that creates immutable sorted maps with an explicit comparator. If the
  comparator has a more general type than the map's keys, such as creating a {@code
  SortedMap<Integer, String>} with a {@code Comparator<Number>}, use the {@link Builder}
  constructor instead.
  
  @throws NullPointerException if {@code comparator} is null