code: def _get_server(self, server_id):
          
  
          if server_id not in self._servers:
              raise ValueError(
                  _format("WBEM server {0!A} not known by subscription manager",
                          server_id))
  
          return self._servers[server_id]
docs: Internal method to get the server object, given a server_id.
  
          Parameters:
  
            server_id (:term:`string`):
              The server ID of the WBEM server, returned by
              :meth:`~pywbem.WBEMSubscriptionManager.add_server`.
  
          Returns:
  
            server (:class:`~pywbem.WBEMServer`):
              The WBEM server.
  
          Raises:
  
              ValueError: server_id not known to subscription manager.