def insert(self, doc, synced=False):
        doc.id = self.get_next_id()
        doc.synced = synced
        try:
            self.db.docs.insert(doc)
        except Exception as e:
            raise DatabaseException(e)
        return doc
def _get(delta, start):
            p = start
            while delta:
                p = p.next
                delta -= 1
            return p.val