AttributeError: 'NoneType' object has no attribute 'decode' during TFLite to ONNX conversion

[kismeter]

Describe the bug

I encountered an error while attempting to convert a TFLite model to ONNX using the tf2onnx tool. using the following command:
python -m tf2onnx.convert --tflite keyword_scrambled.tflite
The error seems to originate from the tf2onnx/tflite_utils.py file, where it attempts to call tensor.Name().decode(). However, tensor appears to be None, resulting in an AttributeError.

Urgency

System information

• OS Platform and Distribution (e.g., Linux Ubuntu 18.04*):
• TensorFlow Version: tf-nightly 2.18.0.dev20240706
• Python version: 3.10.14
• ONNX version (if applicable, e.g. 1.11*): 1.13.0
• ONNXRuntime version (if applicable, e.g. 1.11*): 1.13.0
• tf2onnx: 1.16.1

To Reproduce

1. Install TensorFlow nightly version (2.18.0.dev20240706), ONNX 1.13.0, and tf2onnx 1.16.1.
2. Use tf2onnx.convert to attempt to convert a TensorFlow Lite model to ONNX.
3. The conversion fails with an AttributeError.

Screenshots

Additional context

tflite model from https://github.com/tensorflow/tflite-micro/blob/main/tensorflow/lite/micro/models/keyword_scrambled.tflite

2024-10-21 11:40:04,176 - INFO - Using tensorflow=2.18.0.dev20240706, onnx=1.13.0, tf2onnx=1.16.1/15c810
2024-10-21 11:40:04,176 - INFO - Using opset <onnx, 15>
INFO: Created TensorFlow Lite XNNPACK delegate for CPU.
Traceback (most recent call last):
File "/opt/homebrew/Caskroom/miniforge/base/envs/tf-nightly/lib/python3.10/runpy.py", line 196, in _run_module_as_main
return _run_code(code, main_globals, None,
File "/opt/homebrew/Caskroom/miniforge/base/envs/tf-nightly/lib/python3.10/runpy.py", line 86, in _run_code
exec(code, run_globals)
File "/opt/homebrew/Caskroom/miniforge/base/envs/tf-nightly/lib/python3.10/site-packages/tf2onnx/convert.py", line 714, in
main()
File "/opt/homebrew/Caskroom/miniforge/base/envs/tf-nightly/lib/python3.10/site-packages/tf2onnx/convert.py", line 273, in main
model_proto, _ = _convert_common(
File "/opt/homebrew/Caskroom/miniforge/base/envs/tf-nightly/lib/python3.10/site-packages/tf2onnx/convert.py", line 168, in _convert_common
g = process_tf_graph(tf_graph, const_node_values=const_node_values,
File "/opt/homebrew/Caskroom/miniforge/base/envs/tf-nightly/lib/python3.10/site-packages/tf2onnx/tfonnx.py", line 453, in process_tf_graph
main_g, subgraphs = graphs_from_tflite(tflite_path, input_names, output_names)
File "/opt/homebrew/Caskroom/miniforge/base/envs/tf-nightly/lib/python3.10/site-packages/tf2onnx/tflite_utils.py", line 153, in graphs_from_tflite
parse_tflite_graph(tfl_graph, opcodes, model, prefix, tensor_shapes_from_interpreter)
File "/opt/homebrew/Caskroom/miniforge/base/envs/tf-nightly/lib/python3.10/site-packages/tf2onnx/tflite_utils.py", line 325, in parse_tflite_graph
name = tensor.Name().decode()
AttributeError: 'NoneType' object has no attribute 'decode'