def __init__(self, classifier: "CLASSIFIER_TYPE", x_train: np.ndarray, y_train: np.ndarray) -> None:
        """
        Create an :class:`.ActivationDefence` object with the provided classifier.

        :param classifier: Model evaluated for poison.
        :param x_train: dataset used to train the classifier.
        :param y_train: labels used to train the classifier.
        """
        self.classifier = classifier
        self.x_train = x_train
        self.y_train = y_train

        Create an :class:`.ActivationDefence` object with the provided classifier.

        :param classifier: Model evaluated for poison.
        :param x_train: dataset used to train the classifier.
        :param y_train: labels used to train the classifier.
        
art/defences/detector/poison/poison_filtering_defence.py