code: def test_incorrect_backward_unary():
      # as_grad_stopped() makes backward not corresponding to the mathematical
      # differentiation of the forward computation, which should be detected by
      # check_backward.
      def fprop(xs):
          (x,) = xs
          return ((x * x).as_grad_stopped() + x,)
  
      with pytest.raises(chainerx.GradientCheckError):
          _check_backward_unary(fprop)
  
file_path: chainer/tests/chainerx_tests/unit_tests/test_check_backward.py
imports: import pytest
  import chainerx
label_desc: Use image node_id 3 for calling a global function with example usage: test_incorrect_backward_unary() and returns: unknown