code: def _delete_redundancy_routers(self, context, router_db):
          
          e_context = context.elevated()
          for binding in router_db.redundancy_bindings:
              self.delete_router(e_context, binding.redundancy_router_id)
              LOG.debug("Deleted redundancy router %s",
                        binding.redundancy_router_id)
          if router_db.gw_port_id:
              # delete ha settings and extra port for gateway (VIP) port
              self._delete_ha_group(e_context, router_db.gw_port_id)
docs: To be called in delete_router() BEFORE router has been
          deleted in DB. The router should have not interfaces.