public INDArray confusionMatrix(INDArray labels, INDArray pred, int numClasses) {
    NDValidation.validateNumerical("confusionMatrix", "labels", labels);
    NDValidation.validateNumerical("confusionMatrix", "pred", pred);
    return Nd4j.exec(new org.nd4j.linalg.api.ops.impl.shape.ConfusionMatrix(labels, pred, numClasses))[0];
  }