code: def sky2vec(cls, sky):
          
          theta_phi = cls.sky2ang(sky)
          theta, phi = map(np.array, list(zip(*theta_phi)))
          vec = hp.ang2vec(theta, phi)
          return vec
docs: Convert sky positions in to 3d-vectors on the unit sphere.
  
          Parameters
          ----------
          sky : numpy.array
              Sky coordinates as an array of (ra,dec)
  
          Returns
          -------
          vec : numpy.array
              Unit vectors as an array of (x,y,z)
  
          See Also
          --------
          :func:`AegeanTools.regions.Region.vec2sky`