Fix typing

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

art/attacks/evasion/adversarial_patch/adversarial_patch_pytorch.py

@@ -26,7 +26,7 @@
 import logging
 import math
 from packaging.version import parse
-from typing import Any, TYPE_CHECKING
+from typing import Any, cast, TYPE_CHECKING
 
 import numpy as np
 from tqdm.auto import trange
@@ -513,13 +513,15 @@ def generate(  # type: ignore
 
         if hasattr(self.estimator, "nb_classes"):
 
+            y_array: np.ndarray
+
             if y is None:  # pragma: no cover
                 logger.info("Setting labels to estimator classification predictions.")
-                y_array: np.ndarray = to_categorical(
+                y_array = to_categorical(
                     np.argmax(self.estimator.predict(x=x), axis=1), nb_classes=self.estimator.nb_classes
                 )
             else:
-                y_array: np.ndarray = y
+                y_array = cast(np.ndarray, y)
 
             y = check_and_transform_label_format(labels=y_array, nb_classes=self.estimator.nb_classes)