How to use the phasespace.GenParticle function in phasespace

min_mass = tf.cast(min_mass, tf.float64)
        max_mass = tf.cast(max_mass, tf.float64)
        kstar_width_cast = tf.cast(kstar_width, tf.float64)
        kstar_mass_cast = tf.cast(KSTARZ_MASS, dtype=tf.float64)

        kstar_mass = tf.broadcast_to(kstar_mass_cast, shape=(n_events,))
        if kstar_width > 0:
            kstar_mass = tfp.distributions.TruncatedNormal(loc=kstar_mass,
                                                           scale=kstar_width_cast,
                                                           low=min_mass,
                                                           high=max_mass).sample()
        return kstar_mass

    return GenParticle('B0', B0_MASS).set_children(GenParticle('K*0', mass=kstar_mass)
                                                   .set_children(GenParticle('K+', mass=KAON_MASS),
                                                                 GenParticle('pi-', mass=PION_MASS)),
                                                   GenParticle('gamma', mass=0.0))

def test_name_clashes():
    """Test clashes in particle naming."""
    # In children
    with pytest.raises(KeyError):
        GenParticle('Top', 0).set_children(GenParticle('Kstarz', mass=decays.KSTARZ_MASS),
                                           GenParticle('Kstarz', mass=decays.KSTARZ_MASS))
    # With itself
    with pytest.raises(KeyError):
        GenParticle('Top', 0).set_children(GenParticle('Top', mass=decays.KSTARZ_MASS),
                                           GenParticle('Kstarz', mass=decays.KSTARZ_MASS))
    # In grandchildren
    with pytest.raises(KeyError):
        GenParticle('Top', 0).set_children(GenParticle('Kstarz0', mass=decays.KSTARZ_MASS)
                                           .set_children(GenParticle('K+', mass=decays.KAON_MASS),
                                                         GenParticle('pi-', mass=decays.PION_MASS)),
                                           GenParticle('Kstarz0', mass=decays.KSTARZ_MASS)
                                           .set_children(GenParticle('K+', mass=decays.KAON_MASS),
                                                         GenParticle('pi-_1', mass=decays.PION_MASS)))

masses = tf.broadcast_to(mass, shape=(n_events,))
        if kstar_width > 0:

            masses = tfp.distributions.TruncatedNormal(loc=masses,
                                                       scale=width,
                                                       low=min_mass,
                                                       high=max_mass).sample()
        return masses

    def k1_mass(min_mass, max_mass, n_events):
        return res_mass(K1_MASS, k1_width, min_mass, max_mass, n_events)

    def kstar_mass(min_mass, max_mass, n_events):
        return res_mass(KSTARZ_MASS, kstar_width, min_mass, max_mass, n_events)

    return GenParticle('B+', B0_MASS).set_children(GenParticle('K1+', mass=k1_mass)
                                                   .set_children(GenParticle('K*0', mass=kstar_mass)
                                                                 .set_children(GenParticle('K+', mass=KAON_MASS),
                                                                               GenParticle('pi-', mass=PION_MASS)),
                                                                 GenParticle('pi+', mass=PION_MASS)),
                                                   GenParticle('gamma', mass=0.0))

def test_name_clashes():
    """Test clashes in particle naming."""
    # In children
    with pytest.raises(KeyError):
        GenParticle('Top', 0).set_children(GenParticle('Kstarz', mass=decays.KSTARZ_MASS),
                                           GenParticle('Kstarz', mass=decays.KSTARZ_MASS))
    # With itself
    with pytest.raises(KeyError):
        GenParticle('Top', 0).set_children(GenParticle('Top', mass=decays.KSTARZ_MASS),
                                           GenParticle('Kstarz', mass=decays.KSTARZ_MASS))
    # In grandchildren
    with pytest.raises(KeyError):
        GenParticle('Top', 0).set_children(GenParticle('Kstarz0', mass=decays.KSTARZ_MASS)
                                           .set_children(GenParticle('K+', mass=decays.KAON_MASS),
                                                         GenParticle('pi-', mass=decays.PION_MASS)),
                                           GenParticle('Kstarz0', mass=decays.KSTARZ_MASS)
                                           .set_children(GenParticle('K+', mass=decays.KAON_MASS),
                                                         GenParticle('pi-_1', mass=decays.PION_MASS)))

def test_reset_children():
    """Test when children are set twice."""
    top = GenParticle('Top', 0).set_children(GenParticle('Child1', mass=decays.KSTARZ_MASS),
                                             GenParticle('Child2', mass=decays.KSTARZ_MASS))
    with pytest.raises(ValueError):
        top.set_children(GenParticle('Child3', mass=decays.KSTARZ_MASS),
                         GenParticle('Child4', mass=decays.KSTARZ_MASS))

def test_no_children():
    """Test when no children have been configured."""
    top = GenParticle('Top', 0)
    with pytest.raises(ValueError):
        top.generate(n_events=1)

def test_name_clashes():
    """Test clashes in particle naming."""
    # In children
    with pytest.raises(KeyError):
        GenParticle('Top', 0).set_children(GenParticle('Kstarz', mass=decays.KSTARZ_MASS),
                                           GenParticle('Kstarz', mass=decays.KSTARZ_MASS))
    # With itself
    with pytest.raises(KeyError):
        GenParticle('Top', 0).set_children(GenParticle('Top', mass=decays.KSTARZ_MASS),
                                           GenParticle('Kstarz', mass=decays.KSTARZ_MASS))
    # In grandchildren
    with pytest.raises(KeyError):
        GenParticle('Top', 0).set_children(GenParticle('Kstarz0', mass=decays.KSTARZ_MASS)
                                           .set_children(GenParticle('K+', mass=decays.KAON_MASS),
                                                         GenParticle('pi-', mass=decays.PION_MASS)),
                                           GenParticle('Kstarz0', mass=decays.KSTARZ_MASS)
                                           .set_children(GenParticle('K+', mass=decays.KAON_MASS),
                                                         GenParticle('pi-_1', mass=decays.PION_MASS)))

def test_grandchildren():
    """Test that grandchildren detection is correct."""
    top = GenParticle('Top', 0)
    assert not top.has_children
    assert not top.has_grandchildren
    assert not top.set_children(GenParticle('Child1', mass=decays.KSTARZ_MASS),
                                GenParticle('Child2', mass=decays.KSTARZ_MASS)).has_grandchildren