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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def change_view(self, *args, **kwargs):
 """ If only the singleton instance exists, pass ``True`` for ``singleton`` into the template which will use CSS to hide the "save and add another" button. """

        kwargs.setdefault("extra_context", {})
        kwargs["extra_context"]["singleton"] = self.model.objects.count() == 1
        response = super(SingletonAdmin, self).change_view(*args, **kwargs)
        return self.handle_save(args[0], response)