def to_header(self) -> str:
        """Converts the object back into an HTTP header."""
        if self.date is not None:
            return http.http_date(self.date)
        if self.etag is not None:
            return http.quote_etag(self.etag)
        return ""
Converts the object back into an HTTP header.
src/werkzeug/datastructures/range.py