def save_last_sync(self, ids, process):
        try:
            spec = {'_id': 'last_sync'}
            document = {'$set': {process: ids}}
            self.db.internal.update(spec, document, upsert=True)
        except Exception as e:
            raise DatabaseException(e)
def __add__(self, other):
        assert self.n_classes == other.n_classes, "Number of classes does not match"
        return MulticlassContingencyTable(self.table + other.table,
                                          n_classes=self.n_classes,
                                          class_names=self.class_names)