add dynamic ONNX model input example and test
adds dynamic ONNX model input example and test, use case for e.g. isolation or flavour tagging
basically, what one can do now is if one has a set of Particle objects (FROM) you want some ML model evaluated for that is based on relations to other objects (TO; also in the form of Particle), think like a set of tracks for isolation or FT, and you have a fixed number of features (based on functors) per TO object, you can now have inference for such a model that has a fixed output per FROM object.
Edited by Maarten Van Veghel