code: def write_config_value_to_file(key, value, config_path=None):
      
      if config_path is None:
          config_path = DEFAULT_CONFIG_PATH
  
      # Get existing config.
      config = _get_config_dict_from_file(config_path)
  
      # Add/update the key/value pair.
      config[key] = value
  
      # Create parent directories if they are missing.
      mkdir_parents(os.path.dirname(config_path))
  
      # Write the content
      with open(config_path, "w") as fh:
          json.dump(config, fh, sort_keys=True, indent=2)
  
      # Set 600 permissions on the config file.
      os.chmod(config_path, 33216)
  
      return get_config_value_from_file(key, config_path)
docs: Write key/value pair to config file.