code: def stop_to_stop_networks_by_type(gtfs):
      
      route_type_to_network = dict()
      for route_type in route_types.ALL_ROUTE_TYPES:
          if route_type == route_types.WALK:
              net = walk_transfer_stop_to_stop_network(gtfs)
          else:
              net = stop_to_stop_network_for_route_type(gtfs, route_type)
          route_type_to_network[route_type] = net
      assert len(route_type_to_network) == len(route_types.ALL_ROUTE_TYPES)
      return route_type_to_network
docs: Compute stop-to-stop networks for all travel modes (route_types).
  
      Parameters
      ----------
      gtfs: gtfspy.GTFS
  
      Returns
      -------
      dict: dict[int, networkx.DiGraph]
          keys should be one of route_types.ALL_ROUTE_TYPES (i.e. GTFS route_types)