How to modify graph schedule?

Hi I am new to glow and DNN.
I received the onnx file and tried to compile it. The question here is how to map onnx files to high-level IR.
Looking at it, I could find a way to map high-level IR to low-level IR, but I could not find how to map network files to high-level IR.

Instead of modifying the original neural network file, I want to create a modified graph in the process of reading onnx and making it high-level IR.