Google Sheets App Scripts: Show and Close Sidebar

function showSidebar() {  var authorizationUrl = "...";  var template = HtmlService.createTemplate(    'Click <a href="<?= authorizationUrl ?>" target="_blank">Authorize</a>.');  template.authorizationUrl = authorizationUrl;  var page = template.evaluate();  SpreadsheetApp.getUi().showSidebar(page);}function closeSidebar() {  var html = HtmlService.createHtmlOutput("<script>google.script.host.close();</script>");  SpreadsheetApp.getUi().showSidebar(html);}