<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _ensure_localized(self, arg, ambiguous='raise', nonexistent='raise', from_utc=False):
 """ Ensure that we are re-localized. This is for compat as we can then call this on all datetimelike arrays generally (ignored for Period/Timedelta) Parameters arg : Union[DatetimeLikeArray, DatetimeIndexOpsMixin, ndarray] ambiguous : str, bool, or bool-ndarray, default 'raise' nonexistent : str, default 'raise' from_utc : bool, default False If True, localize the i8 ndarray to UTC first before converting to the appropriate tz. If False, localize directly to the tz. Returns ------- localized array """


        # reconvert to local tz
        tz = getattr(self, 'tz', None)
        if tz is not None:
            if not isinstance(arg, type(self)):
                arg = self._simple_new(arg)
            if from_utc:
                arg = arg.tz_localize('UTC').tz_convert(self.tz)
            else:
                arg = arg.tz_localize(
                    self.tz, ambiguous=ambiguous, nonexistent=nonexistent
                )
        return arg