class_docstr: Test the config system.
class_docstr_tok: ["Test","the","config","system","."]
docstr: Test that environment variables get parsed in the TOML file.
code: def test_parsing_env_vars_in_toml(self):
      """Test that environment variables get parsed in the TOML file."""
      # Some useful variables.
      DEFAULT_VAL, DESIRED_VAL = "Christopher", "Walken"
      DUMMY_DEFINITION = "<test definition>"
  
      # Create a dummy default option.
      config._create_option(
          "_test.tomlTest",
          description="This option tests the TOML parser.",
          default_val=DEFAULT_VAL,
      )
      config.get_config_options(force_reparse=True)
      self.assertEqual(config.get_option("_test.tomlTest"), DEFAULT_VAL)
      self.assertEqual(
          config.get_where_defined("_test.tomlTest"),
          ConfigOption.DEFAULT_DEFINITION,
      )
  
      os.environ["TEST_ENV_VAR"] = DESIRED_VAL
  
      # Override it with some TOML
      NEW_TOML = """
              [_test]
              tomlTest="env:TEST_ENV_VAR"
          """
      config._update_config_with_toml(NEW_TOML, DUMMY_DEFINITION)
      self.assertEqual(config.get_option("_test.tomlTest"), DESIRED_VAL)
      self.assertEqual(
          config.get_where_defined("_test.tomlTest"), DUMMY_DEFINITION
      )
  
imports: import copy
  import os
  import textwrap
  import unittest
  from unittest.mock import MagicMock, mock_open, patch
  import pytest
  from parameterized import parameterized
  from streamlit import config, env_util
  from streamlit.config_option import ConfigOption
  from streamlit.errors import StreamlitAPIException
label_desc: Use image node_id 15 for calling the ConfigTest obj's underlying member method code with example usage: obj.test_parsing_env_vars_in_toml() without return types