code: def get_destinations(self, ascii_listing):
          
          self.destinations = set()
          def collect_destinations(matchobj):
              numbers = matchobj.group("no")
              if numbers:
                  self.destinations.update(set(
                      [n.strip() for n in numbers.split(",")]
                  ))
  
          for line in self._iter_lines(ascii_listing):
              self.renum_regex.sub(collect_destinations, line)
  
          return sorted([int(no) for no in self.destinations if no])
docs: returns all line numbers that are used in a jump.