code: def test_no_output(self):
      chainer.backward([])
      chainer.backward([], [])
  
imports: import unittest
  import mock
  import numpy
  import pytest
  import chainer
  from chainer.backends import cuda
  from chainer import testing
  from chainer.testing import attr
  import chainerx
label_desc: Use image node_id 1 for calling the TestBackward obj's underlying member method code with example usage: obj.test_no_output() without return types