code: def test_string_content(self):
      self.assertEqual(content_str("simple string"), "simple string")
  
imports: import importlib.metadata
  import os
  import sys
  import unittest
  import pytest
  import autogen
  from autogen.code_utils import PATH_SEPARATOR, UNKNOWN, WIN32, content_str, execute_code, extract_code, improve_code, improve_function, infer_lang
label_desc: Use image node_id 1 for calling the TestContentStr obj's underlying member method code with example usage: obj.test_string_content() without return types