Currently, my PR on FlaxVisionEncoderDecoderModel  is not merged to transformers master yet. But I can’t wait to update my poor-french-image-captioning Spaces demo app.
So I need to
git clone https://github.com/ydshieh/transformers.git
cd transformers
git checkout flax_vision_encoder_decoder
pip install --upgrade .[dev]

Is this doable in Spaces currently? I can probably upload a copy of transformers to avoid git  part, but still need  pip install. 
Otherwise, I think I can still figure out a hard way to make the demo work.