code: def d3logpdf_dlink3(self, link_f, y, Y_metadata=None):
          
          N = y.shape[0]
          D = link_f.shape[1]
          d3logpdf_dlink3 = np.zeros((N,D))
          return d3logpdf_dlink3
docs: Third order derivative log-likelihood function at y given link(f) w.r.t link(f)
  
          .. math::
              \\frac{d^{3} \\ln p(y_{i}|\\lambda(f_{i}))}{d^{3}\\lambda(f)} = 0
  
          :param link_f: latent variables link(f)
          :type link_f: Nx1 array
          :param y: data
          :type y: Nx1 array
          :param Y_metadata: Y_metadata not used in gaussian
          :returns: third derivative of log likelihood evaluated at points link(f)
          :rtype: Nx1 array