Python app.db 模块，backref() 实例源码

def on_policy_enable(self, key, enable):
        if not self.policy_enabled and enable:
            self.next_delete = (
                datetime.now(timezone.utc) + self.policy_delete_every)
            self.reason = None
            self.dormant = False
        return enable

    # backref: tokens
    # backref: twitter_archives
    # backref: posts
    # backref: sessions