docs: def conditional_to(self, request):
          """Return a response that is conditional to a given request.
  
          Returns the Response object unchanged, or a new Response object
          with a "304 Not Modified" status code.
          """
          if not self.code == 200:
              return self
  
          request_headers = request.headers
          response_headers = self.headers
  
          if_none_match = request_headers.get('If-None-Match')
          if_modified_since = request_headers.get('If-Modified-Since')
  
          etag_ok, date_ok = False, False
  
          if if_none_match:
              etag = response_headers.get('ETag')
              if etag and match_etag(etag, if_none_match, weak=True):
                  etag_ok = True
  
          if if_modified_since:
              last_modified = response_headers.get('Last-Modified')
              if last_modified:
                  try:
                      modified_ts = httpdate_to_timestamp(last_modified)
                      last_valid_ts = httpdate_to_timestamp(if_modified_since)
                      if modified_ts <= last_valid_ts:
                          date_ok = True
                  except:
                      pass  # Ignore invalid dates
  
          if if_none_match and not etag_ok:
              return self
          elif if_modified_since and not date_ok:
              return self
          elif etag_ok or date_ok:
              headers = filter_304_headers(self.headers.items())
              if 'Date' not in self.headers:
                  headers.append(('Date', datetime_to_httpdate(time.time())))
              return Response(status=304, headers=headers, body='')
          return self