def get_next_id(self):
        try:
            query = {'_id': 'last_id'}
            update = {'$inc': {'id': 1}}
            fn = self.db.internal.find_and_modify
            row = fn(query, update, upsert=True, new=True)
        except Exception as e:
            raise DatabaseException(e)
        return row['id']
def main():
    # Contingency Table from Wilks (2011) Table 8.3
    table = np.array([[50, 91, 71],
                      [47, 2364, 170],
                      [54, 205, 3288]])
    mct = MulticlassContingencyTable(table, n_classes=table.shape[0],
                                     class_names=np.arange(table.shape[0]).astype(str))
    print(mct.peirce_skill_score())
    print(mct.gerrity_score())