if we send a request for getting policy instances for undefined policy type, A1 adaptor would need to return an error message via DMaaP.. but it seems not..
here is info for producing the issue.
output for getpolicytypes ..

—

[
    {
        "body": {
        "output":

{         "CommonHeader":         \{ "APIver": "1.0", "RequestID": "722ee65a-8afd-48df-bf57-c152ae45bacc", "RequestTrack": "no", "SubRequestID": "1", "TimeStamp": "2018-09-10T07:10:05.614Z" }

,
        "Payload": "[*_20010 _*]\n",
              "Status":

             {   "Code": "200", "Value": "getPolicyTypes executed successfully" }

    }
},

request for policy instances for undefined policy type (20012)
{
"body": {
"input": {
"CommonHeader": {
"TimeStamp": "2018-11-30T09:13:37.368Z",
"APIVer": "1.0",
"RequestID": "9d2d790e-a5f0-11e8-98d0-529269fb1459",
"SubRequestID": "1",
"RequestTrack": {},
"Flags": {}
},
"Action": "getPolicyInstances",
"Payload": { "input" :

{ "near-rt-ric-id" : "xxxx:10000", "policy-type-id": "20012" }

}
}
},
"version": "1.0",
"rpc-name": "getPolicyInstances",
"correlation-id": "9d2d790e-a5f0-11e8-98d0-529269fb1459-1",
"type": "request"
}

no response on dmaap..
a1mediator console shows this.. 
{"ts": 1591333737715, "crit": "WARNING", "id": "a1.controller", "mdc": {}, "msg": "Request failed, returning 404: PolicyTypeNotFound()"}
::ffff:76.206.115.146 - - [2020-06-05 05:08:57] "GET /a1-p/policytypes/20012/policies HTTP/1.1" 404 138 0.006617