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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 extend_hit(self, hit_id, number, duration_hours=None):
 """Extend an existing HIT and return an updated description"""

        self.create_additional_assignments_for_hit(hit_id, number)

        if duration_hours is not None:
            self.update_expiration_for_hit(hit_id, duration_hours)

        return self.get_hit(hit_id)