AtomType a1 [N,O;!H0]
AtomType a2 \
 [N,O]
DefineFeature HDonor1 [{a1}]
    Family HBondDonor
    Weights 1.0
EndFeature
DefineFeature HAcceptor1 [{a2}]
    Family \ 
    HBondAcceptor
    Weights 1.0
EndFeature