message: Add type hints to relu_test.py
diff: @@ -5,7 +5,7 @@ from onnx import defs, helper
  class TestRelu(unittest.TestCase):
  - def test_relu(self):
  + def test_relu(self): # type: () -> None
  self.assertTrue(defs.has('Relu'))
  helper.make_node(
  'Relu', ['X'], ['Y'])
  