Fix unicode issue

[gramalingam]

This copilot-suggested fix enabled converting a recent onnx model to onnxscript.

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
685	1	684	2953

View the top 1 failed test(s) by shortest run time

onnxscript.backend.onnx_export_test.TestOnnxBackEnd::test_export2python

Stack Traces | 0.004s run time

onnxscript\backend\onnx_export_test.py:220: in test_export2python
    code = onnx_export.export2python(proto, rename=True, use_operators=True)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript\backend\onnx_export.py:919: in export2python
    return exporter.export(model_onnx, function_name)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript\backend\onnx_export.py:825: in export
    translated_functions.append(self._translate_graph(proto, function_name))
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript\backend\onnx_export.py:736: in _translate_graph
    add(self._translate_graph_body(graph, opsets, indent=indent_level))
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript\backend\onnx_export.py:381: in _translate_graph_body
    pynode = self._translate_node(node, opsets, indent=indent)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript\backend\onnx_export.py:607: in _translate_node
    attributes_str = self._translate_attributes(node)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript\backend\onnx_export.py:397: in _translate_attributes
    if isinstance(value, str, bytes):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
E   TypeError: isinstance expected 2 arguments, got 3

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[justinchuby]

I have seen cases where the string attributes iare used to store binary data (e.g. in the custom Tokenizer op, even though this is invalid onnx). Is this trying to address those cases? If so, I would simply preserve the b-string to avoid accidental modifications.

Related: onnx/ir-py#184

[gramalingam]

I don't know. All I know is that this enabled me to convert a recent model (Word Fluency) into onnxscript so that I could see the control-flow structure of the model in a compact readable format. I don't mind alternatives if they allow me to do this.

[justinchuby]

Right - that's the same model I looked at. Making a suggestion

[justinchuby]

Can you try the current change?