function Sheet(workbook, idNode, node, relationshipsNode) {
    _classCallCheck(this, Sheet);

    this._init(workbook, idNode, node, relationshipsNode);
  }
//  * Creates a new instance of Sheet.
  //  * @param {Workbook} workbook - The parent workbook.
  //  * @param {{}} idNode - The sheet ID node (from the parent workbook).
  //  * @param {{}} node - The sheet node.
  //  * @param {{}} [relationshipsNode] - The optional sheet relationships node.
  //