private int countData(DataList<? extends Data> dataList) {
            int count = 0;
            for (Data data : dataList.asList()) {
                if (data instanceof DataList)
                    count += countData((DataList<?>) data);
                else
                    count++;
            }
            return count;
        }
The prefix "[name] " is prepended to the string data
container-core/src/test/java/com/yahoo/processing/test/ProcessorLibrary.java