code: def l3_tenant_id(cls):
          
          if cls._l3_tenant_uuid is None:
              if hasattr(cfg.CONF.keystone_authtoken, 'project_domain_id'):
                  # TODO(sridar): hack for now to determing if keystone v3
                  # API is to be used.
                  cls._l3_tenant_uuid = cls._get_tenant_id_using_keystone_v3()
              else:
                  cls._l3_tenant_uuid = cls._get_tenant_id_using_keystone_v2()
          return cls._l3_tenant_uuid
docs: Returns id of tenant owning hosting device resources.