docs: public static String resolveWidgetVar(String expression, UIComponent component) {
          UIComponent resolvedComponent = SearchExpressionFacade.resolveComponent(
                  FacesContext.getCurrentInstance(),
                  component,
                  expression);
  
          if (resolvedComponent instanceof Widget) {
              return "PF('" + ((Widget) resolvedComponent).resolveWidgetVar() + "')";
          }
          else {
              throw new FacesException("Component with clientId " + resolvedComponent.getClientId() + " is not a Widget");
          }
      }