code: def test_config_hash():
      root = _create_test_config()
      root.add(
          "test__config_hash",
          "A config var from a test case.",
          configparser.StrParam("test_default"),
      )
  
      h0 = root.get_config_hash()
  
      with root.change_flags(test__config_hash="new_value"):
          assert root.test__config_hash == "new_value"
          h1 = root.get_config_hash()
  
      h2 = root.get_config_hash()
      assert h1 != h0
      assert h2 == h0
  
imports: import configparser
  import io
  import pickle
  import pytest
  from pytensor import configdefaults, configparser
  from pytensor.configdefaults import short_platform
  from pytensor.configparser import ConfigParam
label_desc: Use image node_id 4 for calling a global function with example usage: test_config_hash() without return types