code: def delete_os_dummy_rtr_nwk(self, rtr_id, net_id, subnet_id):
          
          subnet_lst = set()
          subnet_lst.add(subnet_id)
          ret = self.os_helper.delete_intf_router(None, None, rtr_id, subnet_lst)
          if not ret:
              return ret
          return self.os_helper.delete_network_all_subnets(net_id)
docs: Delete the dummy interface to the router.