code: def _setup(self):
          
          settings_module = os.environ.get(ENVIRONMENT_SETTINGS_VARIABLE, 'settings')
          if not settings_module:
              raise ImproperlyConfigured(
                  'Requested settings module points to an empty variable. '
                  'You must either define the environment variable {0} '
                  'or call settings.configure() before accessing the settings.'
                  .format(ENVIRONMENT_SETTINGS_VARIABLE))
  
          self._wrapped = Settings(settings_module, default_settings=global_settings)
docs: Load the settings module pointed to by the environment variable. This
          is used the first time we need any settings at all, if the user has not
          previously configured the settings manually.