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