public static AdaBoost fit(Formula formula, DataFrame data) {
        return fit(formula, data, new Properties());
    }
@Test
    public void testBreastCancer() {
        System.out.println("Breast Cancer");

        MathEx.setSeed(19650218); // to get repeatable results.
        ClassificationValidations<AdaBoost> result = CrossValidation.classification(10, BreastCancer.formula, BreastCancer.data,
                (f, x) -> AdaBoost.fit(f, x, 100, 20, 4, 1));

        System.out.println(result);
        int error = result.rounds.stream().mapToInt(round -> round.metrics.error).sum();
        assertEquals(15, error);
    }