code: def test_handle_double_ref():
      """Test proper handling of double references in dicts"""
      a = {"b": 2, "c": 3}
      d = {"a": a, "d": {"e": a}}
      assert flatten(d) == {"a.b": 2, "a.c": 3, "d.e.b": 2, "d.e.c": 3}
  
label_desc: Use image node_id 2 for calling a global function with example usage: test_handle_double_ref() without return types