docs: def get_response(self, environ=None):
          """Get a list of headers."""
          response = super(SameContentException, self).get_response(
              environ=environ
          )
          if self.etag is not None:
              response.set_etag(self.etag)
          if self.last_modified is not None:
              response.headers['Last-Modified'] = http_date(self.last_modified)
          return response