code: def test_infer_lang():
      assert infer_lang("print('hello world')") == "python"
      assert infer_lang("pip install autogen") == "sh"
  
      # test infer lang for unknown code/invalid code
      assert infer_lang("dummy text") == UNKNOWN
      assert infer_lang("print('hello world'))") == UNKNOWN
  
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 2 for calling a global function with example usage: test_infer_lang() without return types