Selector = function (elements, extendList, condition, index, currentFileInfo, visibilityInfo) {
        this.extendList = extendList;
        this.condition = condition;
        this.evaldCondition = !condition;
        this._index = index;
        this._fileInfo = currentFileInfo;
        this.elements = this.getElements(elements);
        this.mixinElements_ = undefined;
        this.copyVisibilityInfo(visibilityInfo);
        this.setParent(this.elements, this);
    }
An overridden version of the default Object.prototype.toString
which uses additional information to create a helpful message.

@param {Object} options
@returns {string}