code: def test_check_function_nested(self) -> None:
      func_domain = "local"
      func_nested_opset_imports = [
          helper.make_opsetid("", 14),
          helper.make_opsetid(func_domain, 1),
      ]
      # nested identity/add function
      func_nested_identity_add_name = "func_nested_identity_add"
      func_nested_identity_add_inputs = ["a", "b"]
      func_nested_identity_add_outputs = ["c"]
      func_nested_identity_add_nodes = [
          helper.make_node(
              "func_identity", ["a"], ["a1"], domain=func_domain
          ),
          helper.make_node(
              "func_identity", ["b"], ["b1"], domain=func_domain
          ),
          helper.make_node(
              "func_add", ["a1", "b1"], ["c"], domain=func_domain
          ),
      ]
      func_nested_identity_add = helper.make_function(
          func_domain,
          func_nested_identity_add_name,
          func_nested_identity_add_inputs,
          func_nested_identity_add_outputs,
          func_nested_identity_add_nodes,
          func_nested_opset_imports,
      )
      checker.check_function(func_nested_identity_add)
  
imports: import os
  import tempfile
  import unittest
  from typing import Sequence
  import numpy
  import onnx.defs
  import onnx.parser
  from onnx import GraphProto, SparseTensorProto, TensorProto, checker, helper, numpy_helper, shape_inference
label_desc: Use image node_id 5 for calling the TestChecker obj's underlying member method code with example usage: obj.test_check_function_nested() without return types