divergence_coefficient(): Lyubishchev's standardised separation
coefficient D for two groups on continuous features.scatter_ellipse(): fits per-class covariance ellipses (mean, covariance,
sample size).transgression(): detects ellipse overlap via squared Mahalanobis distance
against a chi-squared threshold.classify(): Edgeworth-Pearson multivariate posterior classification of a
new specimen with a numerically stable softmax.