Can not log the credentials

"policy_chain": [
            {
                "name": "logging",
                "version": "builtin",
                "configuration": {
                    "condition": {
                        "combine_op": "and"
                    },
                    "enable_access_logs": true,
                    "custom_logging": "[{{ time_local }}] {{ host }}:{{ server_port }} {{ remote_addr }}:{{ remote_port }} [Original IP {{ headers['X-Forwarded-For'] }} ]  \\\\\\\"{{ request }}\\\\\\\" {{ status }} {{ body_bytes_sent }} ({{ request_time }})  [Credential: {{ credentials['app_id']  }} ]"
                }
            },
            {
                "name": "apicast",
                "version": "builtin",
                "configuration": {}
            }
        ],

{{credentials['app_id']}} is not logged.
[28/Jul/2020:16:18:29 +0000] echo-api.3scale.net:8080 172.17.0.1:51606 [Original IP 1.2.3.4 ]  \\\"GET /employee/tsmwdiko/v1/employee/1160-4FE4-A6E8-FD8073CA07B9?app_id=7cc9f339&app_key=f1147a0a HTTP/1.1\\\" 200 795 (1.163)  [Credential:  ]