code: def test_singular_cpu(self):
      x = chainer.Variable(numpy.zeros((2, 2), dtype=numpy.float32))
      with self.assertRaises(ValueError):
          functions.inv(x)
  
imports: import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer import functions
  from chainer import testing
  from chainer.testing import attr
  from chainer.utils import type_check
label_desc: Use image node_id 3 for calling the InvFunctionRaiseTest obj's underlying member method code with example usage: obj.test_singular_cpu() without return types