code: def diag_port(self, context, port_id, **kwargs):
          
          LOG.info("diag_port %s" % port_id)
          try:
              port = self._client.show_port(port_id)
          except Exception as e:
              msg = "failed fetching downstream port: %s" % (str(e))
              LOG.exception(msg)
              raise IronicException(msg=msg)
          return {"downstream_port": port}
docs: Diagnose a port.
  
          :param context: neutron api request context.
          :param port_id: neutron port id.
          :param kwargs: optional kwargs.
          :raises IronicException: If the client is unable to fetch the
              downstream port for any reason, the exception will be
              logged and IronicException raised.