import IMP.example
(m,c)=IMP.example.create_model_and_particles()

uf= IMP.core.Harmonic(0,1)
df= IMP.core.DistancePairScore(uf)
r= IMP.core.PairRestraint(df, IMP.ParticlePair(c.get_particle(0), c.get_particle(1)))
m.add_restraint(r)