Return ``True`` if `Range` header is present and if underlying
        resource is considered unchanged when compared with `If-Range` header.

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