How to build onnx quantize fp8 Flux model?

I have a question that How Black Forest Lab can export fp8 onnx with their checkpoint like this https://huggingface.co/black-forest-labs/FLUX.1-dev-onnx.

I want to build an Onnx fp8 model from my repo vuongminhkhoi4/Flux_HyperSD . Can you take me a guide or give me code for build this? Thanks a lot!