def get_nbosons(event):
    nbosons = 0
    for genpart in event.GenPart:
        if abs(genpart.pdgId) in [11,12,13,14,15,16,23,24] and genpart.genPartIdxMother==0:
            if abs(genpart.pdgId)<20:
                nbosons += 1
            else:
                nbosons += 2
    return nbosons

def selection(event):
    return True if event.dataset.parent not in "EWKV2Jets" else (event.nGenBosons==1)