code: public static <E> ImmutableSortedSet<E> copyOf(
        Comparator<? super E> comparator, Iterator<? extends E> elements) {
      return new Builder<E>(comparator).addAll(elements).build();
    }
docs: Returns an immutable sorted set containing the given elements sorted by the given {@code
  Comparator}. When multiple elements are equivalent according to {@code compareTo()}, only the
  first one specified is included.
  
  @throws NullPointerException if {@code comparator} or any of {@code elements} is null