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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 get_hours_for_week(self, week_start=None):
 """ Gets all ProjectHours entries in the 7-day period beginning on week_start. """

        week_start = week_start if week_start else self.week_start
        week_end = week_start + relativedelta(days=7)

        return ProjectHours.objects.filter(
            week_start__gte=week_start, week_start__lt=week_end)