code: def _GetRoutingMap(self, router):
      
  
      try:
        routing_map = self._routing_maps_cache.Get(router.__class__)
      except KeyError:
        routing_map = self._BuildHttpRoutingMap(router.__class__)
        self._routing_maps_cache.Put(router.__class__, routing_map)
  
      return routing_map
docs: Returns a routing map for a given router instance.