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 __init__(self, root, cwd, badfn=None, relativeuipath=True):
        self._root = root
        self._cwd = cwd
        if badfn is not None:
            self.bad = badfn
        self._relativeuipath = relativeuipath