code: public Histogram getProbabilityHistogram(int labelClassIdx) {
          String title = "Network Probabilities Histogram - P(class " + labelClassIdx + ") - Data Labelled Class "
                          + labelClassIdx + " Only";
          int[] counts = probHistogramByLabelClass.getColumn(labelClassIdx).dup().data().asInt();
          return new Histogram(title, 0.0, 1.0, counts);
      }
docs: Return a probability histogram of the specified label class index. That is, for label class index i,
  a histogram of P(class_i | input) is returned, only for those examples that are labelled as class i.
  
  @param labelClassIdx Index of the label class to get the histogram for
  @return Probability histogram