code: def get_model(self):
      class Model(chainer.Chain):
          def __init__(self):
              super().__init__()
              with self.init_scope():
                  self.gn = L.GroupNormalization(2)
  
          def forward(self, x):
              return self.gn(x)
  
      return Model()
  
imports: import chainer
  import chainer.functions
  import chainer.links
  from chainer import testing
  import numpy
  from onnx_chainer.testing import input_generator
  from onnx_chainer_tests.helper import get_initializer_names
  from onnx_chainer_tests.helper import ONNXModelTest
label_desc: Use image node_id 1 for calling the TestGroupNormalization obj's underlying member method code with example usage: obj.get_model() and returns: Model, self