code: def get_next_sibling(self):
          
          siblings = self.get_siblings()
          ids = [obj.pk for obj in siblings]
          if self.pk in ids:
              idx = ids.index(self.pk)
              if idx < len(siblings) - 1:
                  return siblings[idx + 1]
docs: :returns:
  
              The next node's sibling, or None if it was the rightmost
              sibling.