code: def set_r_value(self, r_var: str, *, notify_changed=True) -> None:
          
          self.r_var = r_var
          self._description_changed()
          if notify_changed:  # set to False to set the r-value at startup; avoid marking it as a change
              self.__notify_description_changed()
docs: Used to signal changes to the ref var, which are kept in document controller. ugh.