Fix LGTM

Signed-off-by: Beat Buesser <[email protected]>

Author: Beat Buesser

art/attacks/evasion/imperceptible_asr/imperceptible_asr_pytorch.py

@@ -52,6 +52,8 @@ class ImperceptibleASRPytorch(EvasionAttack):
     | Paper link: https://arxiv.org/abs/1903.10346
     """
 
+    import torch
+
     attack_params = EvasionAttack.attack_params + [
         "initial_eps",
         "max_iter_1st_stage",