分页
https://www.jianshu.com/p/0c957c57ae10
关于 follow=true, rule
https://zhuanlan.zhihu.com/p/25650763
关于rule
Each Rule defines a certain behaviour for crawling the site. Rules objects are described below. If multiple rules match the same link, the first one will be used, according to the order they’re defined in this attribute.
further more,
rule (xxxx , callback=F1 ... )
rule (yyyy, callback=F1 ... )
def F1,
def F2