Support document-question-answering ONNX export for vision-encoder-decoder (#1110)
* fix
* support doc question answering ONNX export for vision-encoder-decoder
* fix tests
* hopefully fix!
* fix
* Update optimum/exporters/onnx/base.py
Co-authored-by: Michael Benayoun <mickbenayoun@gmail.com>
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Co-authored-by: Michael Benayoun <mickbenayoun@gmail.com>