private static HttpResponse createResponse(IllegalArgumentException ex) {
        final String message = ex.getMessage() == null ? HttpStatus.BAD_REQUEST.reasonPhrase()
                                                       : ex.getMessage();
        return HttpResponse.of(HttpStatus.BAD_REQUEST, MediaType.PLAIN_TEXT, message);
    }
This only works reliably if maybeMap is from Json, as maps(objects) in Json
can only have string keys.
graphql-protocol/src/main/java/com/linecorp/armeria/server/graphql/protocol/AbstractGraphqlService.java