code: def force_extrapolation(self):
          
          # We use _model here in case the spectrum is redshifted.
          if isinstance(self._model, Empirical1D):
              self._model.fill_value = np.nan
              is_forced = True
          else:
              is_forced = False
  
          return is_forced
docs: Force the underlying model to extrapolate.
  
          An example where this is useful: You create a source spectrum
          with non-default extrapolation behavior and you wish to force
          the underlying empirical model to extrapolate based on nearest point.
  
          .. note::
  
              This is only applicable to `~synphot.models.Empirical1D` model
              and should still work even if the source spectrum has been
              redshifted.
  
          Returns
          -------
          is_forced : bool
              `True` if the model is successfully forced to be extrapolated,
              else `False`.