def to_header(self) -> str:
        """Converts the object back into an HTTP header."""
        ranges = []
        for begin, end in self.ranges:
            if end is None:
                ranges.append(f"{begin}-" if begin >= 0 else str(begin))
            else:
                ranges.append(f"{begin}-{end - 1}")
        return f"{self.units}={','.join(ranges)}"
Converts the object back into an HTTP header.
src/werkzeug/datastructures/range.py