def METHOD_NAME(self, z_trigger: np.ndarray, x_target: np.ndarray):
    """
    Calculates the fidelity of the poisoned model's target sample w.r.t. the original x_target sample
    :param z_trigger: the secret backdoor trigger that will produce the target
    :param x_target: the target to produce when using the trigger
    """
    import tensorflow as tf
    return tf.reduce_mean(
        tf.math.squared_difference(
            tf.dtypes.cast(self.estimator.predict(z_trigger), tf.float64),
            tf.dtypes.cast(x_target, tf.float64),
        )
    )