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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 byweekday(self):
 """ The weekdays where the recurrence will be applied. In RFC5545 this is called BYDAY, but is renamed by dateutil to avoid ambiguity. """

        retval = []
        if self.rule._byweekday:
            retval += [Weekday(day) for day in self.rule._byweekday]
        if self.rule._bynweekday:
            retval += [Weekday(day, n) for day, n in self.rule._bynweekday]
        return retval