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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 monthly_build_list_regex(self):
 """Return the regex for the folder containing builds of a month."""

        # Regex for possible builds for the given date
        return r'nightly/%(YEAR)s/%(MONTH)s/' % {
            'YEAR': self.date.year,
            'MONTH': str(self.date.month).zfill(2)}