code: def test_value_and_grad_np_backend(self):
      n = 10
      vector = gs.ones(n)
      with pytest.raises(RuntimeError):
          gs.autodiff.value_and_grad(lambda v: gs.sum(v**2))(vector)
  
imports: import warnings
  import numpy
  import pytest
  import geomstats.backend
  from geomstats.geometry.grassmannian import Grassmannian
  from geomstats.geometry.special_euclidean import SpecialEuclidean
  from geomstats.test.test_case import TestCase, autograd_and_torch_only, autograd_only, np_only
label_desc: Use image node_id 2 for calling the TestAutodiff obj's underlying member method code with example usage: obj.test_value_and_grad_np_backend() without return types