code: def parent(self):
          
          if self._has_parent is None:
              _parent = self._ctx.backend.get_parent(self._ctx.dev)
              self._has_parent = _parent is not None
              if self._has_parent:
                  self._parent = Device(_parent, self._ctx.backend)
              else:
                  self._parent = None
          return self._parent
docs: Return the parent device.