code: def check_by_definition(self, x):
      ans = F.det(chainer.Variable(x)).data
      y = x[0, 0] * x[1, 1] - x[0, 1] * x[1, 0]
      testing.assert_allclose(ans, y, **self.check_forward_options)
  
imports: import unittest
  import numpy
  import six
  import chainer
  from chainer.backends import cuda
  from chainer import functions
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
  from chainer.utils import type_check
label_desc: Use image node_id 2 for calling the TestDetSmallCase obj's underlying member method code with example usage: obj.check_by_definition(x) without return types