How to use the amuse.ic.plummer.new_plummer_model function in amuse

def test2(self):
        particles=new_plummer_model(10000)
        instance = Agama(type="Multipole", particles=particles)
        result=instance.get_potential_at_point(
            0.|generic_unit_system.length,
            0.|generic_unit_system.length,
            0.|generic_unit_system.length,
            0.|generic_unit_system.length)
        self.assertLess(abs(result/(-16./3/3.1416|
            generic_unit_system.length**2/generic_unit_system.time**2) - 1), 0.04)

        scaleM=1234|units.MSun
        scaleR=5.6 |units.parsec
        converter=nbody_system.nbody_to_si(scaleM,scaleR)
        particles=new_plummer_model(20000, convert_nbody=converter)
        instance = Agama(converter, type="Multipole", particles=particles)
        x=3.|units.parsec
        y=4.|units.parsec

def test2(self):
        particles=new_plummer_model(10000)
        instance = Agama(type="Multipole", particles=particles)
        result=instance.get_potential_at_point(
            0.|generic_unit_system.length,
            0.|generic_unit_system.length,
            0.|generic_unit_system.length,
            0.|generic_unit_system.length)
        self.assertLess(abs(result/(-16./3/3.1416|
            generic_unit_system.length**2/generic_unit_system.time**2) - 1), 0.04)

        scaleM=1234|units.MSun
        scaleR=5.6 |units.parsec
        converter=nbody_system.nbody_to_si(scaleM,scaleR)
        particles=new_plummer_model(20000, convert_nbody=converter)
        instance = Agama(converter, type="Multipole", particles=particles)
        x=3.|units.parsec
        y=4.|units.parsec
        z=5.|units.parsec
        r=(x*x+y*y+z*z)**0.5
        result=instance.get_gravity_at_point(0|units.parsec, x, y, z)
        expected=-constants.G*scaleM/(r*r+(3*3.1416/16*scaleR)**2)**1.5*x
        self.assertLess(abs(result[0]/expected-1), 0.03)
        self.assertLess(abs(result[2]/result[0]-z/x), 0.03)
        instance.stop()