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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 timer_cb(self, timer):
 """Timer callback. Update all our clocks."""

        dt_now = datetime.utcnow().replace(tzinfo=pytz.utc)
        self.logger.debug("timer fired. utc time is '%s'" % (str(dt_now)))

        for clock in self.clocks.values():
            clock.update_clock(dt_now)

        # update clocks approx every second
        timer.start(1.0)