onnx: Optimizer crashes on onnx model converted from Tensorflow graph

Hi, I am trying to invoke the ONNX optimizer following in the instructions in the following post:

https://github.com/onnx/onnx/blob/master/docs/PythonAPIOverview.md#optimizing-an-onnx-model

The ONNX model is converted from a `TensorFlow .pb file:

     onnx_model = tensorflow_graph_to_onnx_model(graph_def, outputs, opset=7,
                             ignore_unimplemented=True)

    all_passes = optimizer.get_available_passes()
    print("Available optimization passes:")
    for p in all_passes:
        print(p)
    print()
    # Apply the optimization on the original model
    passes = ['fuse_consecutive_transposes']

    optimized_onnx_model = optimizer.optimize(onnx_model, passes)

I am getting a crash in the optimizer:

 File "/home/xxx/PycharmProjects/virtualenv/local/lib/python3.5/site-packages/onnx/optimizer.py", line 52, in optimize
    optimized_model_str = C.optimize(model_str, passes)
IndexError: _Map_base::at

onnx version: 1.3.0

onnx-tf verison: 1.1.2

Thanks!