def gradients_XX_diag(self, dL_dKdiag, X):
        raise(NotImplementedError, "This is the diagonal of the second derivative of K wrt X and X2, and not implemented for this kernel")
The diagonal of the second derivative w.r.t. X and X2
dataset/ETHPy150Open SheffieldML/GPy/GPy/kern/src/kern.py/Kern.gradients_XX_diag