How to use the node-opcua-address-space.addElement function in node-opcua-address-space

public  _exposeSubscriptionDiagnostics(subscription: Subscription) {
        debugLog("ServerSession#_exposeSubscriptionDiagnostics");
        assert(subscription.$session === this);
        const subscriptionDiagnosticsArray = this._getSubscriptionDiagnosticsArray();
        const subscriptionDiagnostics = subscription.subscriptionDiagnostics;
        assert(subscriptionDiagnostics.$subscription === subscription);

        if (subscriptionDiagnostics && subscriptionDiagnosticsArray) {
            // xx console.log("GG => ServerSession Exposing subscription diagnostics =>",
            // subscription.id,"on session", session.nodeId.toString());
            addElement(subscriptionDiagnostics, subscriptionDiagnosticsArray);
        }
    }

this.sessionSecurityDiagnostics = sessionSecurityDiagnosticsType.instantiate({
                    browseName: new QualifiedName({ name: "SessionSecurityDiagnostics", namespaceIndex: 0 }),
                    componentOf: this.sessionObject,
                    extensionObject: this._sessionSecurityDiagnostics,
                    minimumSamplingInterval: 2000 // 2 seconds
                }) as UASessionSecurityDiagnostics;
    
                ensureObjectIsSecure(this.sessionSecurityDiagnostics);

                this._sessionSecurityDiagnostics = this.sessionSecurityDiagnostics.$extensionObject as SessionSecurityDiagnosticsDataTypeEx;
                assert(this._sessionSecurityDiagnostics.$session === this);
    
                const sessionSecurityDiagnosticsArray = this.getSessionSecurityDiagnosticsArray();
    
                // add sessionDiagnostics into sessionDiagnosticsArray
                const node = addElement(this._sessionSecurityDiagnostics, sessionSecurityDiagnosticsArray);
                ensureObjectIsSecure(node);

            }
    
        }

});
    
                this.sessionDiagnostics = sessionDiagnosticsVariableType.instantiate({
                    browseName: new QualifiedName({ name: "SessionDiagnostics", namespaceIndex: 0 }),
                    componentOf: this.sessionObject,
                    extensionObject: this._sessionDiagnostics,
                    minimumSamplingInterval: 2000 // 2 seconds
                }) as UASessionDiagnostics;
    
                this._sessionDiagnostics = this.sessionDiagnostics.$extensionObject as SessionDiagnosticsDataTypeEx;
                assert(this._sessionDiagnostics.$session === this);
    
                const sessionDiagnosticsArray = this.getSessionDiagnosticsArray();
    
                // add sessionDiagnostics into sessionDiagnosticsArray
                addElement(this._sessionDiagnostics, sessionDiagnosticsArray);
    
            }
    
        } 
        function createSessionSecurityDiagnosticsStuff(this: ServerSession) {

ServerSession.prototype._exposeSubscriptionDiagnostics = function (subscription) {
    const session = this;
    debugLog("ServerSession#_exposeSubscriptionDiagnostics");
    assert(subscription.$session === session);
    const subscriptionDiagnosticsArray = session._getSubscriptionDiagnosticsArray();
    const subscriptionDiagnostics = subscription.subscriptionDiagnostics;
    assert(subscriptionDiagnostics.$subscription == subscription);

    if (subscriptionDiagnostics && subscriptionDiagnosticsArray) {
        //xx console.log("GGGGGGGGGGGGGGGG => ServerSession Exposing subscription diagnostics =>",subscription.id,"on session", session.nodeId.toString());
        eoan.addElement(subscriptionDiagnostics, subscriptionDiagnosticsArray);
    }
};

ServerEngine.prototype._exposeSubscriptionDiagnostics = function (subscription) {

    debugLog("ServerEngine#_exposeSubscriptionDiagnostics");
    const engine = this;
    const subscriptionDiagnosticsArray = engine._getServerSubscriptionDiagnosticsArray();
    const subscriptionDiagnostics = subscription.subscriptionDiagnostics;
    assert(subscriptionDiagnostics.$subscription == subscription);

    if (subscriptionDiagnostics && subscriptionDiagnosticsArray) {
        //xx console.log("GGGGGGGGGGGGGGGG ServerEngine => Exposing subscription diagnostics =>",subscription.id);
        eoan.addElement(subscriptionDiagnostics, subscriptionDiagnosticsArray);
    }
};
ServerEngine.prototype._unexposeSubscriptionDiagnostics = function (subscription) {

private _exposeSubscriptionDiagnostics(subscription: Subscription): void {

    debugLog("ServerEngine#_exposeSubscriptionDiagnostics");
    const subscriptionDiagnosticsArray = this._getServerSubscriptionDiagnosticsArray();
    const subscriptionDiagnostics = subscription.subscriptionDiagnostics;
    assert((subscriptionDiagnostics as any).$subscription === subscription);
    assert(subscriptionDiagnostics instanceof SubscriptionDiagnosticsDataType);

    if (subscriptionDiagnostics && subscriptionDiagnosticsArray) {
      addElement(subscriptionDiagnostics, subscriptionDiagnosticsArray);
    }
  }