Getting fission multiplicity

Dear G4 team,
I am aware of how to get cross-section inside the simulation with GEANT4 by using

G4HadronicProcess GetCrossSectionDataStore()->GetCrossSection().

However, I would like to get on the same way, the fission multiplicity nu.
I do not know if it exists a method for this, or if I should force the fission cross-section to be infinite. In this last case, I will change the history of my particles which I do not want.

Do you have any idea of how to proceed?
Thanks a lot,