Draft: ONNX functionality for EGM ID NN reweights
- Adding ONNX functionality into HiggsDNA to load pre-trained NN models
- Added preliminary function to load EGM ID NN reweights
- Currently adds per-photon correction factor into photon collection, which is saved in output
- TODO: replace dummy .onnx model with up-to-date network from Paul, and validate correction factors
- TODO: when validated change to standard event weight systematics function
- TODO: split into separate models for EB/EE
- TODO: ensure sum of weights pre and post selection are the same