code: private <S> void printSamples(final S referenceSample,
        final S predictedSample) {
      final String details = "Expected: {\n" + referenceSample
          + "}\nPredicted: {\n" + predictedSample + "}";
      this.printStream.println(details);
    }
docs: Auxiliary method to print expected and predicted samples.
  
  @param referenceSample
  the reference sample
  @param predictedSample
  the predicted sample