code: def parents(self):
          
          if self._parents is None:
              bottomups = tuple(Relationship.bottomup())
  
              self._parents = TermList()
              self._parents.extend(
                  [ other
                      for rship,others in six.iteritems(self.relations)
                          for other in others
                              if rship in bottomups
                  ]
  
              )
  
          return self._parents
docs: ~TermList: The direct parents of the `Term`.