diff --git a/fluid/adversarial/advbox/attacks/iterator_gradientsign.py b/fluid/adversarial/advbox/attacks/iterator_gradientsign.py
index f6cf1d14f12b477ac75530843aab3fea67554b12..3fc96391d2049918e163ba296b749e522375ca57 100644
--- a/fluid/adversarial/advbox/attacks/iterator_gradientsign.py
+++ b/fluid/adversarial/advbox/attacks/iterator_gradientsign.py
@@ -12,7 +12,6 @@ class IteratorGradientSignAttack(Attack):
     This attack was originally implemented by Alexey Kurakin(Google Brain).
     Paper link: https://arxiv.org/pdf/1607.02533.pdf
     """
-
     def _apply(self, image_label, epsilons=100, steps=10):
         """
         Apply the iterative gradient sign attack.