code: def get_refresh_token(self):
          
          try:
              credentials = OAuth2Credentials.from_json(
                  self.credentials_store[g.oidc_id_token['sub']])
              return credentials.refresh_token
          except KeyError:
              logger.debug("Expired ID token, credentials missing",
                           exc_info=True)
              return None
docs: Method to return the current requests' refresh_token.
  
          :returns: Access token or None
          :rtype: str
  
          .. versionadded:: 1.2