docs: private List<Map<StreamStateHandle, OperatorStateHandle>> initMergeMapList(List<List<OperatorStateHandle>> parallelSubtaskStates) {
  
  		int parallelism = parallelSubtaskStates.size();
  
  		final List<Map<StreamStateHandle, OperatorStateHandle>> mergeMapList = new ArrayList<>(parallelism);
  
  		for (List<OperatorStateHandle> previousParallelSubtaskState : parallelSubtaskStates) {
  			mergeMapList.add(previousParallelSubtaskState.stream()
  				.collect(Collectors.toMap(OperatorStateHandle::getDelegateStateHandle, Function.identity())));
  		}
  
  		return mergeMapList;
  	}