docs: function getFirstSupportedAscendant(xtypes) {
        var arr = xtypes.split('/');
        for (var i = arr.length; i >= 0; i--) {
          var xtype = arr[i];
          if (this.supportedXTypes.includes(xtype)) {
            return xtype;
          }
        }
        throw new Error(xtypes + ' not supported');
      }