Function spherical_harmonic

pub fn spherical_harmonic(
    l: usize,
    m: isize,
    costheta: Float,
    phi: Float,
) -> Complex<Float>

Computes the spherical harmonic $Y_{\ell}^m(\theta, \phi)$ (given $\cos\theta$). Note that this formulation includes the Condon-Shortley phase.