Merge branch 'development_audio_backdoor' of github.com:Swanand-Kadhe/adversarial-robustness-toolbox into development_audio_backdoor

merge remote branch into local

Author: Swanand-Kadhe

tests/attacks/evasion/test_sign_opt.py

@@ -23,7 +23,7 @@
 from art.estimators.estimator import BaseEstimator
 from art.estimators.classification.classifier import ClassifierMixin
 
-from tests.attacks.utils import backend_targeted_tabular, backend_untargeted_tabular, backend_targeted_images
+from tests.attacks.utils import backend_targeted_tabular, backend_untargeted_tabular
 from tests.attacks.utils import back_end_untargeted_images, backend_test_classifier_type_check_fail
 from tests.utils import ARTTestException