def predict_sign(self, vec: np.ndarray) -> np.ndarray:
        """
        Predicts the inputs by binary classifier and outputs -1 and 1 instead of 0 and 1.

        :param vec: An input array.
        :return: An array of -1/1 predictions.
        """

        preds = self.estimator.model.predict(vec)
        return 2 * preds - 1

        Predicts the inputs by binary classifier and outputs -1 and 1 instead of 0 and 1.

        :param vec: An input array.
        :return: An array of -1/1 predictions.
        
art/attacks/poisoning/poisoning_attack_svm.py