code: def test_nesting_two_levels(self):
      experiment = {
          "democ": {
              "_name": "DemoC",
              "demob": {
                  "_name": "DemoB",
                  "attrb": 10,
                  "demoa": {
                      "_name": "DemoA",
                      "simple_int": "$simple_int",
                  },
              },
          },
          "simple_int": 2,
      }
  
      e = ExperimentConfig(experiment)
      self.assertEqual(e["democ"].demob.attrb, 10)
      self.assertEqual(e["democ"].attrc, 3)
      self.assertEqual(e["democ"].demob.demoa.simple_int, 2)
  
imports: import unittest
  from pathlib import Path
  from typing import Any, Dict, List
  from transfer_nlp.plugins.config import CallableInstantiationError, ExperimentConfig, LoopInConfigError, UnknownPluginException, UnknownReferenceError, register_plugin
label_desc: Use image node_id 15 for calling the RegistryTest obj's underlying member method code with example usage: obj.test_nesting_two_levels() without return types