code: public final Ix<T> orderBy(Comparator<? super T> comparator) {
          return new IxOrderBy<T, T>(this, IdentityHelper.<T>instance(), nullCheck(comparator, "comparator is null"), 1);
      }
docs: Orders elements according to the comparator.
  <p>
  The result's iterator() doesn't support remove().
  @param comparator the comparator comparing two elements; if it returns a negative value,
  the first element will be before the second; if it returns a positive value,
  the first element will be after the second.
  @return the new Ix instance
  @throws NullPointerException if comparator is null
  @since 1.0
  @see #orderBy()
  @see #orderByReverse(Comparator)