Inviter delegate cannot work

[ReadingCommando]

        inviter = new Inviter(userAgent, targetURI);
        inviter.delegate = {
            onAck: (response) => {                   
                console.log(response);
            },
            onInfo: (response) => {                   
                console.log(response);
            },
            onBye: (response) => {         
                console.log(response);
            },
        };

cannot trigger method onInfo or onBye