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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 _prev_month(self):
 """Updated calendar to show the previous month."""

        self._canvas.place_forget()

        self._date = self._date - self.timedelta(days=1)
        self._date = self.datetime(self._date.year, self._date.month, 1)
        self._build_calendar()