def _read_data(self, spider, request):
        key = self._request_key(request)
        db = self.db
        tkey = '%s_time' % key
        if tkey not in db:
            return  # not found

        ts = db[tkey]
        if 0 < self.expiration_secs < float(ts) - time():
            return  # expired

        return pickle.loads(db['%s_data' % key])
dataset/ETHPy150Open scrapy/scrapy/scrapy/extensions/httpcache.py/DbmCacheStorage._read_data/swapped operands of `-`