code: def test_from_fallback_device(self, backend_config):
      # Preparation: it depends on ChainerxDevice.fallback_device
      tmp_device = backend.ChainerxDevice(
          chainerx.get_device(backend_config.chainerx_device)
      )
      fallback_device = tmp_device.fallback_device
  
      # Test
      device = backend.ChainerxDevice.from_fallback_device(
          fallback_device
      )
      self.check_device(device, backend_config)
      assert device.fallback_device == fallback_device
  
imports: import unittest
  import numpy
  import chainer
  from chainer import backend
  from chainer.backends import cuda
  from chainer import testing
  from chainer.testing import attr
  import chainerx
label_desc: Use image node_id 4 for calling the TestChainerxDevice obj's underlying member method code with example usage: obj.test_from_fallback_device(backend_config) without return types