default AGG fetchSession(final K key,
                             final Instant sessionStartTime,
                             final Instant sessionEndTime) {
        throw new UnsupportedOperationException(
            "This API is not supported by this implementation of ReadOnlySessionStore.");
    }
Get the value of key from a single session.

@param key              the key to fetch
@param sessionStartTime start timestamp of the session
@param sessionEndTime   end timestamp of the session
@return The value or {@code null} if no session with the exact start and end timestamp exists
        for the given key
@throws NullPointerException If {@code null} is used for any key.
streams/src/main/java/org/apache/kafka/streams/state/ReadOnlySessionStore.java