code: public function compound(Comparator $secondaryComparator) : Ordering
      {
          return Ordering::from(Collections::comparatorFrom(
              function ($object1, $object2) use ($secondaryComparator) {
                  $res = $this->compare($object1, $object2);
                  return $res !== 0 ? $res : $secondaryComparator->compare($object1, $object2);
              }
          ));
      }
docs: Returns an ordering which first uses the ordering this, but which in the event of a "tie",
  then delegates to secondaryComparator.
  
  @param Comparator $secondaryComparator
  @return Ordering