How to use the less/tree.Selector function in less

tree.mixin.Call = function MixinCall(elements, args, index) {
    this.selector = new(tree.Selector)(elements);
    this.arguments = args;
    this.index = index;
};
tree.mixin.Call.prototype = {

this.rulesets().forEach(function (rule) {
            if (rule !== self) {
                for (var j = 0; j < rule.selectors.length; j++) {
                    if (match = selector.match(rule.selectors[j])) {
                        if (selector.elements.length > 1) {
                            Array.prototype.push.apply(rules, rule.find(
                                new(tree.Selector)(selector.elements.slice(1)), self));
                        } else {
                            rules.push(rule);
                        }
                        break;
                    }
                }
            }
        });
        return this._lookups[key] = rules;

selector: function () {
                var sel, e, elements = [], match;

                while (e = $(this.element)) { elements.push(e) }

                if (elements.length > 0) { return new(tree.Selector)(elements) }
            },
            tag: function () {

this.rulesets().forEach(function (rule) {
            if (rule !== self) {
                for (var j = 0; j < rule.selectors.length; j++) {
                    if (match = selector.match(rule.selectors[j])) {
                        if (selector.elements.length > 1) {
                            Array.prototype.push.apply(rules, rule.find(
                                new(tree.Selector)(selector.elements.slice(1)), self));
                        } else {
                            rules.push(rule);
                        }
                        break;
                    }
                }
            }
        });
        return this._lookups[key] = rules;

tree.mixin.Call = function MixinCall(elements, args, index) {
    this.selector = new(tree.Selector)(elements);
    this.arguments = args;
    this.index = index;
};
tree.mixin.Call.prototype = {

tree.mixin.Call = function MixinCall(elements, args, index) {
    this.selector = new(tree.Selector)(elements);
    this.arguments = args;
    this.index = index;
};
tree.mixin.Call.prototype = {

selector: function () {
                var sel, e, elements = [], match;

                while (e = $(this.element)) { elements.push(e) }

                if (elements.length > 0) { return new(tree.Selector)(elements) }
            },
            tag: function () {