Function predict_probability 

pub fn predict_probability(
    model: &SvmModel,
    x: &[SvmNode],
) -> Option<(f64, Vec<f64>)>

Predict with probability estimates.

Returns Some((label, probs)) where probs[i] is the estimated probability of class model.label[i]. Returns None when the model was not trained with probability support.

• C-SVC / ν-SVC: requires model.prob_a and model.prob_b. Uses Platt scaling on pairwise decision values, then multiclass_probability for k > 2.
• One-class: requires model.prob_density_marks. Returns [p, 1-p] via density-mark lookup.
• SVR: probability prediction is not supported (returns None).

Matches LIBSVM’s svm_predict_probability.