docs: def refresh(self):
          """Refresh the server and it's child objects.
  
          This method removes all the cache information in the server
          and it's child objects, and fetches the information again from
          the server using hpssacli/ssacli command.
  
          :raises: HPSSAOperationError, if hpssacli/ssacli operation failed.
          """
          config = self._get_all_details()
  
          raid_info = _convert_to_dict(config)
          self.controllers = []
  
          for key, value in raid_info.items():
              self.controllers.append(Controller(key, value, self))
  
          self.last_updated = time.time()