@classmethod
def _bpr_evaluation(cls, prediction, reference):
    """Return boundary precision, recall, and F-score for segmentations."""
    rec_s, rec_t = cls._boundary_recall(prediction, reference)
    pre_s, pre_t = cls._boundary_recall(reference, prediction)
    rec = rec_s / rec_t
    pre = pre_s / pre_t
    f = 2.0 * pre * rec / (pre + rec)
    return pre, rec, f
