public Response process(Request request, Execution execution) {
            request.properties().set("appendage", request.properties().getInteger("appendage") + 1);
            Response response = execution.process(request);

            // Modify the response
            StringData first = (StringData) response.data().get(0);
            StringData third = (StringData) response.data().get(2);
            first.setString(first.toString() + ", " + third.toString());
            response.data().asList().remove(2);
            return response;
        }
Makes some modifications to the request, passes it on and finally removes one data item from the response
container-core/src/test/java/com/yahoo/processing/test/ProcessorLibrary.java