docs: public static <I, O> CrossValidationEvaluation<I, O> kFold(
  			Collection<Example<I, O>> data, int k) {
  		Preconditions.checkNotNull(data);
  		Preconditions.checkArgument(k > 1);
  
  		int numTrainingPoints = data.size();
  		List<Collection<Example<I, O>>> folds = Lists.newArrayList();
  		for (List<Example<I, O>> fold : Iterables.partition(data, (int) Math.ceil(numTrainingPoints / k))) {
  			folds.add(fold);
  		}
  		
  		return new CrossValidationEvaluation<I, O>(folds);
  	}