How to use the node-opcua-service-call.CallResponse function in node-opcua-service-call

self.performMessageTransaction(request, function (err, response) {

        /* istanbul ignore next */
        if (err) {
            return callback(err);
        }
        assert(response instanceof call_service.CallResponse);
        callback(null, isArray ? response.results : response.results[0]);

    });

const TransferSubscriptionsRequest = subscription_service.TransferSubscriptionsRequest;
const TransferSubscriptionsResponse = subscription_service.TransferSubscriptionsResponse;

const CreateMonitoredItemsRequest = subscription_service.CreateMonitoredItemsRequest;
const CreateMonitoredItemsResponse = subscription_service.CreateMonitoredItemsResponse;

const ModifyMonitoredItemsRequest = subscription_service.ModifyMonitoredItemsRequest;
const ModifyMonitoredItemsResponse = subscription_service.ModifyMonitoredItemsResponse;
const MonitoredItemModifyResult = subscription_service.MonitoredItemModifyResult;

const MonitoredItemCreateResult = subscription_service.MonitoredItemCreateResult;
const SetPublishingModeRequest = subscription_service.SetPublishingModeRequest;
const SetPublishingModeResponse = subscription_service.SetPublishingModeResponse;

const CallRequest = call_service.CallRequest;
const CallResponse = call_service.CallResponse;

const ReadRequest = read_service.ReadRequest;
const ReadResponse = read_service.ReadResponse;

const WriteRequest = write_service.WriteRequest;
const WriteResponse = write_service.WriteResponse;

const ReadValueId = read_service.ReadValueId;

const HistoryReadRequest = historizing_service.HistoryReadRequest;
const HistoryReadResponse = historizing_service.HistoryReadResponse;

const BrowseRequest = browse_service.BrowseRequest;
const BrowseResponse = browse_service.BrowseResponse;

const BrowseNextRequest = browse_service.BrowseNextRequest;