HepMC3 event record library

Pythia8 → include Relation

File in interfaces/pythia8/include/Pythia8Includes file in include
Pythia8ToHepMC3.hHepMC3 / GenEvent.h
Pythia8ToHepMC3.hHepMC3 / GenParticle.h
Pythia8ToHepMC3.hHepMC3 / GenVertex.h