docs: def _is_range_request_processable(self, environ):
          """Return ``True`` if `Range` header is present and if underlying
          resource is considered unchanged when compared with `If-Range` header.
          """
          return (
              "HTTP_IF_RANGE" not in environ
              or not is_resource_modified(
                  environ,
                  self.headers.get("etag"),
                  None,
                  self.headers.get("last-modified"),
                  ignore_if_range=False,
              )
          ) and "HTTP_RANGE" in environ