code: def add(self,
              parameters,
              abort_on_invalid=True,
              send_from_cache=True):
          
  
          # Verify that we already know our assigned subscription_id
          assert self.subscription_id != -1
  
          if not parameters:
              return
  
          options = web_pb2.ParameterSubscriptionRequest()
          options.subscriptionId = self.subscription_id
          options.abortOnInvalid = abort_on_invalid
          options.sendFromCache = send_from_cache
          options.id.extend(_build_named_object_ids(parameters))
  
          self._manager.send('subscribe', options)
docs: Add one or more parameters to this subscription.
  
          :param parameters: Parameter(s) to be added
          :type parameters: Union[str, str[]]
          :param bool abort_on_invalid: If ``True`` one invalid parameter
                                        means any other parameter in the
                                        request will also not be added
                                        to the subscription.
          :param bool send_from_cache: If ``True`` the last processed parameter
                                       value is sent from parameter cache.
                                       When ``False`` only newly processed
                                       parameters are received.