Run the attack on a specific target class.
    :param x: tf Tensor. The input example.
    :param target_y: tf Tensor. The attacker's desired target class.
    Returns:
      A targeted adversarial example, intended to be classified as the target class.

def attack_class(self, x, target_y):
    """
    Run the attack on a specific target class.
    :param x: tf Tensor. The input example.
    :param target_y: tf Tensor. The attacker's desired target class.
    Returns:
      A targeted adversarial example, intended to be classified as the target class.
    """
    adv = self.base_attacker.generate(x, y_target=target_y, **self.params)
    return adv