Before revision:  To improve the  robustness, adversarial data augmentation (ADA) has been widely adopted , which attempts to cover more search space of adversarial attacks by adding the adversarial examples during training.
After revision:  To improve the robustness, adversarial data augmentation (ADA) has been widely adopted , which attempts to cover more search space of adversarial attacks by adding textual adversarial examples during training.