code: def refresh_persistent_maps(self):
          
          for robot in self._robots:
              resp2 = (requests.get(urljoin(
                  self.ENDPOINT,
                  'users/me/robots/{}/persistent_maps'.format(robot.serial)),
                  headers=self._headers))
              resp2.raise_for_status()
              self._persistent_maps.update({robot.serial: resp2.json()})
docs: Get information about persistent maps of the robots.
  
          :return: