code: def test_list(self) -> None:
      self.assertIs(
          extract_nested_type(
              SampleOuterConfig,
              ["my_dict_of_schemas", "key", "my_help_text"],
          ),
          str,
      )
  
imports: from enum import Enum
  from typing import ClassVar, Dict, List, Optional, Union
  from unittest import main, TestCase
  import attr
  from torchbiggraph.schema import Dumper, extract_nested_type, inject_nested_value, Loader, Schema, schema, unpack_optional
label_desc: Use image node_id 3 for calling the TestExtractNestedType obj's underlying member method code with example usage: obj.test_list() without return types