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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 set_dhw_on(self, until=None):
 """Set DHW to on, either indefinitely, or until a specified time. When On, the DHW controller will work to keep its target temperature at/above its target temperature. After the specified time, it will revert to its scheduled behaviour. """


        time_until = None if until is None else until.strftime(
            '%Y-%m-%dT%H:%M:%SZ')

        self._set_dhw(status="Hold", mode="DHWOn", next_time=time_until)