How to use the node-opcua-client.TimestampsToReturn.Both function in node-opcua-client

public monitor_item(treeItem: any) {

        if (!this.subscription) return;
        const node = treeItem.node;

        this.subscription.monitor({
            nodeId: node.nodeId,
            attributeId: AttributeIds.Value
            //, dataEncoding: { namespaceIndex: 0, name:null }
        }, {
            samplingInterval: 1000,
            discardOldest: true,
            queueSize: 100
        },
            TimestampsToReturn.Both,
            (err: Error | null, monitoredItem: ClientMonitoredItem) => {

                if (err) {
                    console.log("cannot create monitored item", err.message);
                    return;
                }

                node.monitoredItem = monitoredItem;

                const monitoredItemData = [node.browseName, node.nodeId.toString(), "Q"];

                this.monitoredItemsListData.push(monitoredItemData);

                this.emit("monitoredItemListUpdated", this.monitoredItemsListData);
                //   xxx                monitoredItemsList.setRows(monitoredItemsListData);

attributeId: AttributeIds.Value,
                nodeId: resolveNodeId("ns=3;s=AirConditioner_3.Temperature")
            },
            {
                attributeId: AttributeIds.Value,
                nodeId: resolveNodeId("ns=3;s=AirConditioner_4.Temperature")
            }
        ];

        const optionsGroup = {
            discardOldest: true,
            queueSize: 1,
            samplingInterval: 10
        };

        const monitoredItemGroup = ClientMonitoredItemGroup.create(subscription, itemsToMonitor, optionsGroup, TimestampsToReturn.Both);

        // subscription.on("item_added",function(monitoredItem){
        monitoredItemGroup.on("initialized", async () => {
            console.log(" Initialized !");
        });

        monitoredItemGroup.on("changed", (monitoredItem: ClientMonitoredItemBase, dataValue: DataValue, index: number) => {
            console.log("Changed on ", index, dataValue.value.toString());
        });

        await new Promise((resolve) => setTimeout(resolve, 1000000));

        await monitoredItemGroup.terminate();

        await session.close();
        await client.disconnect();

discardOldest: true,
            queueSize: 100,
            samplingInterval: 100,

            filter: new DataChangeFilter({
                deadbandType: DeadbandType.Absolute,
                deadbandValue: 0.1,
                trigger: DataChangeTrigger.StatusValueTimestamp
            })
        };
        const itemToMonitor1: ReadValueIdLike = {
            attributeId: AttributeIds.Value,
            nodeId: "ns=1;s=FanSpeed"
        };

        const item1 = await subscription.monitor(itemToMonitor1, parameters1, TimestampsToReturn.Both);

        console.log(" Item1 = ", item1.result!.statusCode.toString());

        item1.on("changed", (dataValue: DataValue) => {
            console.log(" Value1 has changed : ", dataValue.toString());
        });
        const itemToMonitor2: ReadValueIdLike = {
            attributeId: AttributeIds.EventNotifier,
            nodeId: "i=2258"
        };
        const parameters2: MonitoringParametersOptions = {
            discardOldest: true,
            filter: new EventFilter({}),
            queueSize: 100,
            samplingInterval: 0
        };