def METHOD_NAME(self):
    mf = scf.ROKS(mol).density_fit ()
    mf.xc = 'b3lypg'
    mf.conv_tol = 1e-14
    e0 = mf.kernel()
    mf_grad = mf.nuc_grad_method ()
    g = mf_grad.kernel()
    mf_scanner = mf.as_scanner()
    e1 = mf_scanner('''O    0.   0.       0.
                    H     0.8  0.3      0.2
                    H    0.   -0.758   0.587
                    H    0.   0.757    0.587''')
    e2 = mf_scanner('''O    0.   0.       0.
                    H     0.8  0.3      0.2
                    H    0.   -0.756   0.587
                    H    0.   0.757    0.587''')
    self.assertAlmostEqual(g[2,1], (e2-e1)/2e-3*lib.param.BOHR, 4)