def _unpickle_classifier(file_name: str) -> "CLASSIFIER_NEURALNETWORK_TYPE":
        """
        Unpickles classifier using the filename provided. Function assumes that the pickle is in
        `art.config.ART_DATA_PATH`.

        :param file_name: Path of the pickled classifier relative to `ART_DATA_PATH`.
        :return: The loaded classifier.
        """
        full_path = os.path.join(config.ART_DATA_PATH, file_name)
        logger.info("Loading classifier from %s", full_path)
        with open(full_path, "rb") as f_classifier:
            loaded_classifier = pickle.load(f_classifier)
            return loaded_classifier

        Unpickles classifier using the filename provided. Function assumes that the pickle is in
        `art.config.ART_DATA_PATH`.

        :param file_name: Path of the pickled classifier relative to `ART_DATA_PATH`.
        :return: The loaded classifier.
        
art/defences/detector/poison/activation_defence.py