code: def _CreateRoutePatternsFolder(self, parent, route,
                                     style_id=None, visible=True):
      
      pattern_id_to_trips = route.GetPatternIdTripDict()
      if not pattern_id_to_trips:
        return None
  
      # sort by number of trips using the pattern
      pattern_trips = pattern_id_to_trips.values()
      pattern_trips.sort(lambda a, b: cmp(len(b), len(a)))
  
      folder = self._CreateFolder(parent, 'Patterns', visible)
      for n, trips in enumerate(pattern_trips):
        trip_ids = [trip.trip_id for trip in trips]
        name = 'Pattern %d (trips: %d)' % (n+1, len(trips))
        description = 'Trips using this pattern (%d in total): %s' % (
            len(trips), ', '.join(trip_ids))
        placemark = self._CreatePlacemark(folder, name, style_id, visible,
                                          description)
        coordinates = [(stop.stop_lon, stop.stop_lat)
                       for stop in trips[0].GetPattern()]
        self._CreateLineString(placemark, coordinates)
      return folder
docs: Create a KML Folder containing placemarks for each pattern in the route.
  
      A pattern is a sequence of stops used by one of the trips in the route.
  
      If there are not patterns for the route then no folder is created and None
      is returned.
  
      Args:
        parent: The parent ElementTree.Element instance.
        route: The transitfeed.Route instance.
        style_id: The id of a style to use if not None.
        visible: Whether the folder is initially visible or not.
  
      Returns:
        The Folder ElementTree.Element instance or None if there are no patterns.