code: def setUp(self):
      class Model(chainer.Chain):
          def __init__(self):
              super(Model, self).__init__()
  
          def __call__(self, x1, x2):
              return F.concat((x1, x2))
  
      self.model = Model()
      self.x1 = input_generator.increasing(2, 5)
      self.x2 = input_generator.increasing(2, 4)
  
imports: import chainer
  import chainer.functions
  from chainer import testing
  import numpy
  import onnx
  import pytest
  from onnx_chainer import export
  from onnx_chainer.testing import input_generator
  from onnx_chainer_tests.helper import ONNXModelChecker
  from onnx_chainer_tests.helper import ONNXModelTest
label_desc: Use image node_id 1 for calling the TestConcat obj's underlying member method code with example usage: obj.setUp() and returns: F