def _get_tzinfo(tz_expr: Optional[TZ_EXPR]) -> dt_tzinfo:
        """Get normalized tzinfo object from various inputs."""
        if tz_expr is None:
            return dateutil_tz.tzutc()
        if isinstance(tz_expr, dt_tzinfo):
            return tz_expr
        else:
            try:
                return parser.TzinfoParser.parse(tz_expr)
            except parser.ParserError:
                raise ValueError(f"{tz_expr!r} not recognized as a timezone.")
Get normalized tzinfo object from various inputs.
arrow/arrow.py