code: def get_subnet_cidr(self, subnet_id):
          
          try:
              subnet_list = self.neutronclient.list_subnets(id=subnet_id)
              subnet_dat = subnet_list.get('subnets')[0]
              return subnet_dat.get('cidr')
          except Exception as exc:
              LOG.error("Failed to list subnet for ID %(subnet)s, "
                        "exc %(exc)s", {'subnet': subnet_id, 'exc': exc})
              return None
docs: retrieve the CIDR associated with a subnet, given its ID.