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:rtype: Collection.Iterable
collect_num æªå¿ç­äº len(collections)ïŒæ¯åŠ:
https://www.zhihu.com/question/20064699/answer/13855720
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@property
def collections(self):

    import time
    gotten_feed_num = 20
    offset = 0
    data = {'method': 'next', '_xsrf': self.xsrf}
    while (gotten_feed_num >= 10):
        data['params'] = ('{"answer_url":    %d,"offset":    %d}' % (self.id, offset))
        res = self._session.post(url=Get_Collection_Url, data=data)
        gotten_feed_num = len(res.json()['msg'])
        offset += gotten_feed_num
        soup = BeautifulSoup(''.join(res.json()['msg']))
        for zm_item in soup.find_all('div', class_='zm-item'):
            url = (Zhihu_URL + zm_item.h2.a['href'])
            name = zm_item.h2.a.text
            links = zm_item.div.find_all('a')
            owner = Author(links[0]['href'], session=self._session)
            follower_num = int(links[1].text.split()[0])
            (yield Collection(url, owner=owner, name=name, follower_num=follower_num, session=self._session))
        time.sleep(0.2)
