code: def xyz2lonlat(x,y,z):
      
  
      xs = np.array(x)
      ys = np.array(y)
      zs = np.array(z)
  
      lons = np.arctan2(ys, xs)
      lats = np.arcsin(zs)
  
      return lons, lats
docs: Convert x,y,z representation of points *on the unit sphere* of the
      spherical triangulation to lon / lat (radians).
  
      Note - no check is made here that (x,y,z) are unit vectors