Tuning ValueHolder as I could not find better option to generate the double-underscore methods.

tests/util/test_compat.py

@@ -21,4 +21,3 @@ def test_deprecated_alias():
 
     with pytest.warns(DeprecationWarning):
         foo()
-

tests/util/test_objects.py

@@ -35,6 +35,7 @@ def test_wrapper_name():
 
 def test_valueholder():
     x = ValueHolder(42)
+
     assert x == 42
     x += 1
     assert x == 43