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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def in_timezone(self, tz):
 # type: (Union[str, Timezone]) -> DateTime """ Set the instance's timezone from a string or object. """

        tz = pendulum._safe_timezone(tz)

        return tz.convert(self, dst_rule=pendulum.POST_TRANSITION)