function HeadersUI(nestedRowsPlugin, hotInstance) {
    var _this;

    (0, _classCallCheck2.default)(this, HeadersUI);
    _this = (0, _possibleConstructorReturn2.default)(this, (0, _getPrototypeOf2.default)(HeadersUI).call(this, nestedRowsPlugin, hotInstance));
    /**
     * Reference to the DataManager instance connected with the Nested Rows plugin.
     *
     * @type {DataManager}
     */

    _this.dataManager = _this.plugin.dataManager; // /**
    //  * Level cache array.
    //  *
    //  * @type {Array}
    //  */
    // this.levelCache = this.dataManager.cache.levels;

    /**
     * Reference to the CollapsingUI instance connected with the Nested Rows plugin.
     *
     * @type {CollapsingUI}
     */

    _this.collapsingUI = _this.plugin.collapsingUI;
    /**
     * Cache for the row headers width.
     *
     * @type {null|Number}
     */

    _this.rowHeaderWidthCache = null;
    /**
     * Reference to the TrimRows instance connected with the Nested Rows plugin.
     *
     * @type {TrimRows}
     */

    _this.trimRowsPlugin = nestedRowsPlugin.trimRowsPlugin;
    return _this;
  }
CSS classes used in the row headers.

@type {Object}