default KeyValueIterator<Windowed<K>, V> backwardAll() {
        throw new UnsupportedOperationException();
    }
Gets all the key-value pairs in the existing windows in backward order
with respect to time (from end to beginning of time).

@return a backward iterator over windowed key-value pairs {@code <Windowed<K>, value>}, from the end to beginning of time.
@throws InvalidStateStoreException if the store is not initialized
streams/src/main/java/org/apache/kafka/streams/state/ReadOnlyWindowStore.java