def set_forward_mode(self, mode: str) -> None:
        """
        Helper function to set the forward mode of the model

        :param mode: either concrete or abstract signifying how to run the forward pass
        """
        assert mode in {"concrete", "abstract"}
        self.forward_mode = mode

        Helper function to set the forward mode of the model

        :param mode: either concrete or abstract signifying how to run the forward pass
        
art/estimators/certification/deep_z/pytorch.py