Suppress test failure for wala#340.

Author: khatchad

com.ibm.wala.cast.python.ml.test/source/com/ibm/wala/cast/python/ml/test/TestTensorflow2Model.java

@@ -2202,7 +2202,11 @@ public void testGradient()
     test("tf2_test_gradient.py", "f", 1, 1, Map.of(2, Set.of(TENSOR_2_NONE_FLOAT32)));
   }
 
-  @Test
+  /**
+   * Should not throw an {@link IllegalArgumentException} once https://github.com/wala/ML/issues/340
+   * is fixed.
+   */
+  @Test(expected = IllegalArgumentException.class)
   public void testGradient2()
       throws ClassHierarchyException, IllegalArgumentException, CancelException, IOException {
     test("tf2_test_gradient2.py", "f", 1, 1, Map.of(2, Set.of(MNIST_INPUT)));