@Override
        public void restore(Map<String, Object> state) {
            countMap = (ConcurrentHashMap<String, Integer>) state.get("CountMap");
        }
Implementation of {@link WindowProcessor} which represent a Window operating based on frequency of incoming events.
Implementation uses a counting algorithm based on Misra-Gries counting algorithm
modules/siddhi-core/src/main/java/io/siddhi/core/query/processor/stream/window/FrequentWindowProcessor.java