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 __expectation_step(self):
        self.__gaussians = [ [] for _ in range(self.__amount_clusters) ]
        for index in range(self.__amount_clusters):
            self.__gaussians[index] = gaussian(self.__data, self.__means[index], self.__variances[index])