code: def api_url(self):
          
          if not self._api_url:
              error_msg = (
                  f"Email is enabled but API_URL is not set. "
                  f"See settings.{self.api_url_attr}"
              )
              try:
                  self._api_url = getattr(settings, self.api_url_attr)
              except AttributeError:
                  raise EmailNotEnabledError(error_msg, code="api_url_attribute_error")
              else:
                  if not self._api_url:
                      raise EmailNotEnabledError(error_msg, code="api_url_is_none")
          return self._api_url
docs: Returns the api_url or None.