Fix LGTM alerts

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

Author: Beat Buesser

art/estimators/certification/randomized_smoothing/numpy.py

@@ -28,7 +28,7 @@
 from art.estimators.certification.randomized_smoothing.randomized_smoothing import RandomizedSmoothingMixin
 from art.estimators.classification import ClassifierMixin, ClassGradientsMixin
 import logging
-from typing import List, Union, TYPE_CHECKING
+from typing import List, Union, TYPE_CHECKING, Tuple
 
 if TYPE_CHECKING:
     from art.utils import CLASSIFIER_LOSS_GRADIENTS_TYPE
@@ -69,6 +69,10 @@ def __init__(
         )
         self.classifier = classifier
 
+    @property
+    def input_shape(self) -> Tuple[int, ...]:
+        return self.classifier.input_shape
+
     def _predict_classifier(self, x: np.ndarray, batch_size: int) -> np.ndarray:
         """
         Perform prediction for a batch of inputs.