code: def alpha(self, x, y, kwargs, k=None):
          
          return self.lens_model.alpha(x, y, kwargs, k=k)
docs: deflection angles
  
          :param x: x-position (preferentially arcsec)
          :type x: numpy array
          :param y: y-position (preferentially arcsec)
          :type y: numpy array
          :param kwargs: list of keyword arguments of lens model parameters matching the lens model classes
          :param k: only evaluate the k-th lens model
          :return: deflection angles in units of arcsec