code: def compare_root_path(path_cost1, path_cost2, bridge_id1, bridge_id2,
                            port_id1, port_id2):
          
          result = Stp._cmp_value(path_cost1, path_cost2)
          if not result:
              result = Stp._cmp_value(bridge_id1, bridge_id2)
              if not result:
                  result = Stp._cmp_value(port_id1, port_id2)
          return result
docs: Decide the port of the side near a root bridge.
              It is compared by the following priorities.
               1. root path cost
               2. designated bridge ID value
               3. designated port ID value