docs: private boolean containsKey(K key, int keyGroupIndex, N namespace) {
  
  		checkKeyNamespacePreconditions(key, namespace);
  
  		Map<N, Map<K, S>> namespaceMap = getMapForKeyGroup(keyGroupIndex);
  
  		if (namespaceMap == null) {
  			return false;
  		}
  
  		Map<K, S> keyedMap = namespaceMap.get(namespace);
  
  		return keyedMap != null && keyedMap.containsKey(key);
  	}