def METHOD_NAME(self, request, *args, **kwargs):
    super().METHOD_NAME(request, *args, **kwargs)
    # The query argument ``upgraded=true`` is used as a the callback
    # URL for stripe checkout, see `self.redirect_to_checkout`.
    if request.GET.METHOD_NAME('upgraded') == 'true':
        messages.success(
            self.request,
            _('Your plan has been upgraded!')
        )
    form = self.get_form()
    context = self.get_context_data(form=form)
    return self.render_to_response(context)