def get_last_tid(self):
        try:
            spec = {'tid': {'$gt': 0}}
            sort = [('tid', -1)]
            row = self.db.docs.find_one(spec, sort=sort)
        except Exception as e:
            raise DatabaseException(e)
        if row:
            return row['tid']
        return 0
def permutation_subjects(y):
    """Permute class labels of Contextual Disorder dataset.
    """
    y_perm = np.random.randint(0, 2, len(y)/2)
    y_perm = np.concatenate((y_perm, np.logical_not(y_perm).astype(int)))
    return y_perm