message: Remove usage of onnx_pb2
diff: @@ -22,7 +22,7 @@ M = 10
  S = 5
  const2_np = np.random.randn(S, S)
  const2_onnx = onnx.helper.make_tensor("const2",
  - onnx.onnx_pb2.TensorProto.FLOAT,
  + onnx.TensorProto.FLOAT,
  (S, S),
  const2_np.flatten().astype(float))
  