Sets the cache, if needed.

def process_response(self, request, response):
        """Sets the cache, if needed."""
        if not hasattr(request, '_cache_update_cache') or not request._cache_update_cache:
            # We don't need to update the cache, just return.
            return response
        if request.method != 'GET':
            # This is a stronger requirement than above. It is needed
            # because of interactions between this middleware and the
            # HTTPMiddleware, which throws the body of a HEAD-request
            # away before this middleware gets a chance to cache it.
            return response
        if not response.status_code == 200:
            return response
        # Try to get the timeout from the "max-age" section of the "Cache-
        # Control" header before reverting to using the default cache_timeout
        # length.
        timeout = get_max_age(response)
        if timeout == None:
            timeout = self.cache_timeout
        elif timeout == 0:
            # max-age was set to 0, don't bother caching.
            return response
        patch_response_headers(response, timeout)
        if timeout:
            cache_key = learn_cache_key(request, response, timeout, self.key_prefix)
            cache.set(cache_key, response, timeout)
            logging.debug("UpdateCacheMiddleware: setting %s -> %s params are: %s" % (cache_key, request.path, get_cache_key_parameters(request)))
        return response