Where do I find setUserInfo(), to set the required information of JWT?

Where do I found the API of setUserInfo()., so that I can understand it much more better or if anyone could explain me ?

 function generateToken(user){
        return jwt.sign(user, authConfig.secret, {
            expiresIn: 10080
        });
    }

    function setUserInfo(request){
        return {
            _id: request._id,
            email: request.email,
            role: request.role
        };
    }

via Aditya Jain