OpenNMT-tf onnx export ?

[flutter-painter]

Based on OpenNMT/OpenNMT-py#638
I suppose this is not possible to export to onnx using OpenNMT-tf either,
But since libs are different and the onnx repo is different I had to ask.

I followed onnx doc
and run :

python -m tf2onnx.convert --saved-model pathto/toy-ende_dir/ --output dst/path/model.onnx --opset 13

=> error : 2024-01-14 16:35:24,876 - ERROR - rewriter <function rewrite_single_direction_lstm at 0x7fe2828c2f70>: exception graph input 'length' not exist

I also tried running it for tflite :

python -m tf2onnx.convert --tflite pathto/toy-ende_lite/opennmt.tflite --output dst/path/model.onnx --opset 13

=> ValueError: Received a shape scalar with unknown static value. A static value of '-1' is required to represent an unknown shape.