            overriding the response_redirect_class attribute.
  
          - ETags: If the USE_ETAGS setting is set, ETags will be calculated from
            the entire page content and Not Modified responses will be returned
            appropriately.
      """
  
      response_redirect_class = http.HttpResponsePermanentRedirect
  
      def process_request(self, request):
 
</s> remove     If-Modified-Since, the response is replaced by an HttpNotModified.
 </s> add     If-Modified-Since, the response is replaced by an HttpNotModified. An ETag
    header is added if needed. </s> remove Handles conditional GET operations. If the response has a ``ETag`` or
 </s> add Handles conditional GET operations. If the response doesn't have an ``ETag``
header, the middleware adds one if needed. If the response has a ``ETag`` or
          appropriately. USE_ETAGS is deprecated in favor of
          ConditionalGetMiddleware.
            overriding the response_redirect_class attribute.
  
          - ETags: If the USE_ETAGS setting is set, ETags will be calculated from
            the entire page content and Not Modified responses will be returned
          appropriately. USE_ETAGS is deprecated in favor of
          ConditionalGetMiddleware.
      """
  
      response_redirect_class = http.HttpResponsePermanentRedirect
  
      def process_request(self, request):
keep keep keep keep replace keep keep keep keep keep
 Fixed #26447 -- Deprecated settings.USE_ETAGS in favor of ConditionalGetMiddleware. 
django/middleware/common.py