def _get_label_proportions(self, dataset):
        pos, neg = [], []
        # split examples into positives and negatives so we know the proportions
        for example in dataset:
            if not example[-1]:
                neg.append(example)
            else:
                pos.append(example)
        num_pos = len(pos) / len(dataset)
        num_neg = len(neg) / len(dataset)
        return num_pos, num_neg