code: def set_restricted(self, obj, restricted):
          
          if restricted:
              self._restricted.add(obj)
          elif obj in self._restricted:
              self._restricted.remove(obj)
docs: Set the restriction on the given object.
  
          You can use this to signal that a certain function is restricted.
          Then you can query the restriction later with :meth:`Reftrack.is_restricted`.
  
          :param obj: a hashable object
          :param restricted: True, if you want to restrict the object.
          :type restricted: :class:`bool`
          :returns: None
          :rtype: None
          :raises: None