How to use the primeng/dom.DomHandler.addMultipleClasses function in primeng

enableModality() {
        if (!this.mask) {
            this.mask = document.createElement('div');
            this.mask.style.zIndex = String(parseInt(this.container.style.zIndex) - 1);
            DomHandler.addMultipleClasses(this.mask, 'ui-widget-overlay ui-dialog-mask');
            document.body.appendChild(this.mask);
            DomHandler.addClass(document.body, 'ui-overflow-hidden');

            if(this.blockScroll) {
                DomHandler.addClass(document.body, 'ui-overflow-hidden');
            }
        }
    }