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 usage_iter(root):
    root = os.path.abspath(root)
    root_size = get_folder_size(root)
    root_string = "{0}\n{1}".format(root, root_size)
    yield [root_string, None, root_size]