def METHOD_NAME(self):
    sim = rebound.Simulation()
    sim.integrator = "leapfrog"
    sim.collision  = "linetree"
    sim.configure_box(100)
    sim.dt = 10
    sim.add(r=1,x=0)
    sim.add(r=1,x=2.1,vx=1)
    sim.integrate(10)