def is_cached_response_valid(self, cachedresponse, response, request):
        # Use the cached response if the new response is a server error,
        # as long as the old response didn't specify must-revalidate.
        if response.status >= 500:
            cc = self._parse_cachecontrol(cachedresponse)
            if b'must-revalidate' not in cc:
                return True

        # Use the cached response if the server says it hasn't changed.
        return response.status == 304
dataset/ETHPy150Open scrapy/scrapy/scrapy/extensions/httpcache.py/RFC2616Policy.is_cached_response_valid/original