trainable variables fix

Author: LukeWood

keras_cv/models/object_detection/retina_net/retina_net_test.py

@@ -210,9 +210,9 @@ def test_weights_contained_in_trainable_variables(self):
         _ = retina_net(xs)
         variable_names = [x.name for x in retina_net.trainable_variables]
         # classification_head
-        self.assertIn('RetinaNet/prediction_head/conv2d_8/kernel:0', variable_names)
+        self.assertIn("RetinaNet/prediction_head/conv2d_8/kernel:0", variable_names)
         # box_head
-        self.assertIn('RetinaNet/prediction_head_1/conv2d_11/kernel:0', variable_names)
+        self.assertIn("RetinaNet/prediction_head_1/conv2d_11/kernel:0", variable_names)
 
     def test_weights_change(self):
         bounding_box_format = "xywh"