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 __update_covariance(self, means, rc, mc):
        covariance = 0.0
        for index_point in range(len(self.__data)):
            deviation = numpy.array([self.__data[index_point] - means])
            covariance += rc[index_point] * deviation.T.dot(deviation)