code: public InternalTimersSnapshot<K, N> snapshotTimersForKeyGroup(int keyGroupIdx) {
  		return new InternalTimersSnapshot<>(
  			keySerializer,
  			namespaceSerializer,
  			eventTimeTimersQueue.getSubsetForKeyGroup(keyGroupIdx),
  			processingTimeTimersQueue.getSubsetForKeyGroup(keyGroupIdx));
  	}
docs: Snapshots the timers (both processing and event time ones) for a given {@code keyGroupIdx}.
  
  @param keyGroupIdx the id of the key-group to be put in the snapshot.
  @return a snapshot containing the timers for the given key-group, and the serializers for them