How to use the plasmapy.particles.integer_charge function in plasmapy

>>> fundamental_electron_collision_freq(0.1 * u.eV, 1e6 / u.m ** 3, 'p', V = c / 100)
    
    >>> fundamental_electron_collision_freq(100 * u.eV, 1e20 / u.m ** 3, 'p', coulomb_log = 20)
    

    See Also
    --------
    collision_frequency
    fundamental_ion_collision_freq
    """
    # specify to use electron thermal velocity (most probable), not based on reduced mass
    V = _replaceNanVwithThermalV(V, T_e, m_e)

    species = [ion, "e-"]
    Z_i = particles.integer_charge(ion)
    nu = collision_frequency(
        T_e, n_e, species, z_mean=Z_i, V=V, method=coulomb_log_method
    )
    coeff = 4 / np.sqrt(np.pi) / 3

    # accounting for when a Coulomb logarithm value is passed
    if np.any(coulomb_log):
        cLog = Coulomb_logarithm(
            T_e, n_e, species, z_mean=Z_i, V=V, method=coulomb_log_method
        )
        # dividing out by typical Coulomb logarithm value implicit in
        # the collision frequency calculation and replacing with
        # the user defined Coulomb logarithm value
        nu_mod = nu * coulomb_log / cLog
        nu_e = coeff * nu_mod
    else:

>>> fundamental_ion_collision_freq(100 * u.eV, 1e20 / u.m ** 3, 'p', coulomb_log=20)
    

    See Also
    --------
    collision_frequency
    fundamental_electron_collision_freq
    """
    m_i = particles.particle_mass(ion)
    species = [ion, ion]

    # specify to use ion thermal velocity (most probable), not based on reduced mass
    V = _replaceNanVwithThermalV(V, T_i, m_i)

    Z_i = particles.integer_charge(ion)

    nu = collision_frequency(
        T_i, n_i, species, z_mean=Z_i, V=V, method=coulomb_log_method
    )
    # factor of 4 due to reduced mass in bperp and the rest is
    # due to differences in definitions of collisional frequency
    coeff = np.sqrt(8 / np.pi) / 3 / 4

    # accounting for when a Coulomb logarithm value is passed
    if np.any(coulomb_log):
        cLog = Coulomb_logarithm(
            T_i, n_i, species, z_mean=Z_i, V=V, method=coulomb_log_method
        )
        # dividing out by typical Coulomb logarithm value implicit in
        # the collision frequency calculation and replacing with
        # the user defined Coulomb logarithm value