Feature request: ONNX Export to older file versions/opsets

[amittere]

Intro

ML.NET supports exporting trained models to the ONNX file format, but only allows export to the latest version/opset. The version of the exported model can also change as ML.NET is updated, which can break compatibility with other toolsets that only support older ONNX versions.

Feature Request

• Support exporting models to older ONNX versions and opsets (ONNX version 1.4, opset 9 or older)

Use case

We would like to run a model trained with ML.NET on Windows devices using the inbox Windows ML runtime, but it does not support the latest ONNX versions which ML.NET exports to.

Workarounds

• Exported models can be converted using the ONNX Version Converter, but it does not work on all models.
• Models can also be hand-edited.