code: def test_circular_reference():
      assert copy(obj4())
      obj4_copy = dill.loads(dill.dumps(obj4()))
      assert (
          type(obj4_copy)
          is type(obj4_copy).__init__.__closure__[0].cell_contents
      )
      assert (
          type(obj4_copy.b)
          is type(obj4_copy.b).__init__.__closure__[0].cell_contents
      )
  
imports: import dill
  from functools import partial
  import warnings
label_desc: Use image node_id 6 for calling a global function with example usage: test_circular_reference() without return types