code: def average(self, dt=None):
          
          if dt is None:
              dt = Date.today()
  
          return self.add(days=int(self.diff(dt, False).in_days() / 2))
docs: Modify the current instance to the average
          of a given instance (default now) and the current instance.
  
          :type dt: Date or date
  
          :rtype: Date