'Make DeleteModel options for proxy models.'

def generate_deleted_proxies(self):

    deleted = set(self.old_proxy_keys).difference(self.new_proxy_keys)
    for (app_label, model_name) in sorted(deleted):
        model_state = self.from_state.models[(app_label, model_name)]
        assert model_state.options.get('proxy')
        self.add_operation(app_label, operations.DeleteModel(name=model_state.name))
