How to use the CSOM SP.Publishing.Variations.getPeerUrl method?

In this code, I am trying to get the corresponding french URL variation. I am using this CSOM api

https://msdn.microsoft.com/en-us/library/office/jj954403.aspx

But I can't figure out how to use it. Does anyone know?

This doesn't seem to be defined in the Publishing object.

.Variations

Thanks

    var ctx = SP.ClientContext.get_current();    var site = ctx.get_site();    var rootWeb = site.get_rootWeb();    var webProperties = rootWeb.get_allProperties();        ctx.load(site);    ctx.load(rootWeb);    ctx.load(webProperties);    ctx.executeQueryAsync(            function() {            var varLabelsListId = webProperties.get_item('_VarLabelsListId');            var labelsList = rootWeb.get_lists().getById(varLabelsListId);            var labelItems = labelsList.getItems(SP.CamlQuery.createAllItemsQuery());            ctx.load(labelItems);            ctx.executeQueryAsync(                            function() {                    var url = rootWeb.get_serverRelativeUrl();                    var object = new SP.Publishing.Variations.getPeerUrl(url, "en-US");                                    },                function() {                }            );        },        function() {        }    );