def METHOD_NAME(l1, l2, alpha=1., beta=1.,
               prefac=1./(4*np.pi), chi_power=6):
    lfac = 1/((l1+0.5)**alpha*(l2+0.5)**beta)
    xpn = alpha+beta-chi_power+1
    chifac = (CHIMAX**xpn-CHIMIN**xpn)/xpn
    return lfac*chifac*prefac