class_docstr: Test the config system.
class_docstr_tok: ["Test","the","config","system","."]
code: def test_is_manually_set(self):
      config._set_option("browser.serverAddress", "some.bucket", "test")
      self.assertEqual(
          True, config.is_manually_set("browser.serverAddress")
      )
  
      config._set_option(
          "browser.serverAddress", "some.bucket", "<default>"
      )
      self.assertEqual(
          False, config.is_manually_set("browser.serverAddress")
      )
  
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 27 for calling the ConfigTest obj's underlying member method code with example usage: obj.test_is_manually_set() without return types