code: def add_neighbours(self):
          
          time_delta = 1 << (2*(IntervalSet.HPY_MAX_ORDER - self.max_order))
  
          intervals_arr = self._interval_set._intervals
          intervals_arr[:, 0] = np.maximum(intervals_arr[:, 0] - time_delta, 0)
          intervals_arr[:, 1] = np.minimum(intervals_arr[:, 1] + time_delta, (1 << 58) - 1)
  
          self._interval_set = IntervalSet(intervals_arr)
docs: Add all the pixels at max order in the neighbourhood of the moc