default KeyValueIterator<Windowed<K>, AGG> backwardFetch(final K keyFrom, final K keyTo) {
        throw new UnsupportedOperationException(
            "This API is not supported by this implementation of ReadOnlySessionStore.");
    }
Retrieve all aggregated sessions for the given range of keys. This iterator must be closed
after use.
<p>
For each key, the iterator guarantees ordering of sessions, starting from the newest/latest
available session to the oldest/earliest session.

@param keyFrom first key in the range to find aggregated session values for
A null value indicates a starting position from the first element in the store.
@param keyTo   last key in the range to find aggregated session values for
A null value indicates that the range ends with the last element in the store.
@return backward KeyValueIterator containing all sessions for the provided key, from newest
to oldest session.
streams/src/main/java/org/apache/kafka/streams/state/ReadOnlySessionStore.java