def get_last_tid(self):
        try:
            spec = {'tid': {'$gt': 0}}
            sort = [('tid', -1)]
            row = self.db.docs.find_one(spec, sort=sort)
        except Exception as e:
            raise DatabaseException(e)
        if row:
            return row['tid']
        return 0
def get_snapshot(self, snapshot_id):
        """Returns the details of a single snapshot."""
        url = "snapshots/%s" % str(snapshot_id)
        resp, body = self.get(url)
        body = json.loads(body)
        return resp, body['snapshot']