code: def get_notify_observers_kwargs(self):
          
          return {
              'u_new': self._u_new,
              'x_new': self._x_new,
              'y_new': self._y_new,
              'z_new': self._z,
              'xi': self._xi,
              'sigma': self._sigma,
              't': self._t_new,
              'idx': self.idx,
          }
docs: Return the mapping between the metrics call and the iterated
          variables.
  
          Return
          ----------
          notify_observers_kwargs: dict,
             the mapping between the iterated variables.