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

font: function () {
                var value = [], expression = [], weight, shorthand, font, e;

                while (e = $(this.shorthand) || $(this.entity)) {
                    expression.push(e);
                }
                value.push(new(tree.Expression)(expression));

                if ($(',')) {
                    while (e = $(this.expression)) {
                        value.push(e);
                        if (! $(',')) { break }
                    }
                }
                return new(tree.Value)(value, $(this.important));
            },

eval: function (env) {
        if (this.value.length === 1) {
            return this.value[0].eval(env);
        } else {
            return new(tree.Value)(this.value.map(function (v) {
                return v.eval(env);
            }));
        }
    },
    toCSS: function () {

value: function () {
                var e, expressions = [], important;

                while (e = $(this.expression)) {
                    expressions.push(e);
                    if (! $(',')) { break }
                }
                important = $(this.important);

                if (expressions.length > 0) {
                    return new(tree.Value)(expressions, important);
                }
            },
            important: function () {

font: function () {
                var value = [], expression = [], weight, shorthand, font, e;

                while (e = $(this.shorthand) || $(this.entity)) {
                    expression.push(e);
                }
                value.push(new(tree.Expression)(expression));

                if ($(',')) {
                    while (e = $(this.expression)) {
                        value.push(e);
                        if (! $(',')) { break }
                    }
                }
                return new(tree.Value)(value, $(this.important));
            },

tree.Rule = function Rule(name, value, index) {
    this.name = name;
    this.value = (value instanceof tree.Value) ? value : new(tree.Value)([value]);
    this.index = index;

    if (name.charAt(0) === '@') {
        this.variable = true;
    } else { this.variable = false }
};
tree.Rule.prototype.toCSS = function (env) {

eval: function (env) {
        if (this.value.length === 1) {
            return this.value[0].eval(env);
        } else {
            return new(tree.Value)(this.value.map(function (v) {
                return v.eval(env);
            }));
        }
    },
    toCSS: function (env) {

tree.Rule = function Rule(name, value, index) {
    this.name = name;
    this.value = (value instanceof tree.Value) ? value : new(tree.Value)([value]);
    this.index = index;

    if (name.charAt(0) === '@') {
        this.variable = true;
    } else { this.variable = false }
};
tree.Rule.prototype.toCSS = function () {

value: function () {
                var e, expressions = [], important;

                while (e = $(this.expression)) {
                    expressions.push(e);
                    if (! $(',')) { break }
                }
                important = $(this.important);

                if (expressions.length > 0) {
                    return new(tree.Value)(expressions, important);
                }
            },
            important: function () {

value: function () {
                var e, expressions = [], important;

                while (e = $(this.expression)) {
                    expressions.push(e);
                    if (! $(',')) { break }
                }
                important = $(this.important);

                if (expressions.length > 0) {
                    return new(tree.Value)(expressions, important);
                }
            },
            important: function () {

tree.Rule = function Rule(name, value, index) {
    this.name = name;
    this.value = (value instanceof tree.Value) ? value : new(tree.Value)([value]);
    this.index = index;

    if (name.charAt(0) === '@') {
        this.variable = true;
    } else { this.variable = false }
};
tree.Rule.prototype.toCSS = function () {