code: def is_ancestor(self, child_key_name, ancestor_key_name):
          
  
          # all keys are descendents of None
          if ancestor_key_name is None:
              return True
  
          one_up_parent = self.dct[child_key_name]['parent']
          if child_key_name == ancestor_key_name:
              # debatable semantics, but a person lies in his/her own
              # ancestry tree
              return True
          elif one_up_parent is None:
              return False
          else:
              return self.is_ancestor(one_up_parent, ancestor_key_name)
docs: Returns True if ancestor lies in the ancestry tree of child.