Trouble importing FaceONNX detector model: Only tensor indices is valid

[SimonBrandner]

Describe the bug

Error during importing the detector model:

ERROR burn_import::logger: PANIC => panicked at /home/simon/Data1/GIT/Rust/burn/crates/burn-import/src/onnx/dim_inference.rs:820:14:
Only tensor indices is valid    

To Reproduce

1. Download detector model from https://drive.google.com/file/d/1tB7Y5l5Jf2270IisgSZ3rbCQs0-pkNIQ/view?usp=drive_link
2. Move the file to src/model/detector.onnx
3. Add this to build.rs

	ModelGen::new()
		.input("src/model/detector.onnx")
		.out_dir("model/")
		.run_from_script();

4. Build and see error

What I've figured out so far

• There is something going on when updating the gather outputs: https://github.com/tracel-ai/burn/blob/main/crates/burn-import/src/onnx/dim_inference.rs#L812

[laggui]

As you correctly pointed out the issue is with the gather node.

We check for the inputs to make sure they are in accordance with the spec, but when checking for the indices we expect a tensor but your model uses a scalar (rank 0 tensor) - which is still valid according to the spec but currently will run into issues with the rest of the codegen for Burn (see issue #1689).

[laggui]

Also I just realized your model was generated with an older opset (v9) and we might not support all of the ops there. Right now the ops we have should support the latest ops at opset 13. Some also have support for older opset but not all (e.g., Slice which I see in your model is opset v1 and we don't parse the attributes).

The ONNX spec is large and our bandwidth for that is a bit limited.