code: def _save_config(self, filename=None):
          
          if filename is None:
              filename = self._config_filename
          parent_path = os.path.dirname(filename)
          if not os.path.isdir(parent_path):
              os.makedirs(parent_path)
          with open(filename, "w") as configfile:
              self._config.write(configfile)
docs: Save the given user configuration.