https://github.com/livid/v2ex/blob/master/topic.py#L1118
#1130~1134行
q = db.GqlQuery("SELECT * FROM Reply WHERE num = :1", int(reply_num))
if q[0]:
reply = q[0]
topic = reply.topic
node = topic.node
#问1134行 为什么不需要先在数据库中获得?因为整个topic对象都存储在reply.topic中吗?