How to add sign function to ONNX?

It looks like the sign function is not supported in ONNX, and therefore, not implemented in PyTorch. However, sign is an ATen operator (defined in VariableType.h) and I’m hoping I can add support for it to ONNX and PyTorch.

Can you share some pointers to how I can add support for sign function?

It looks like implementing the function in Experimental is one of the options, but I couldn’t find a good reference for adding functions to Experimental.