Compute spherical harmonics.
This is a ufunc and may take scalar or array arguments like any other ufunc. The inputs will be broadcasted against each other.
Parameters :  m : int
n : int
theta : float
phi : float


Returns :  y_mn : complex float

Notes
There are different conventions for the meaning of input arguments theta and phi. We take theta to be the azimuthal angle and phi to be the polar angle. It is common to see the opposite convention  that is theta as the polar angle and phi as the azimuthal angle.