I have a google doc template file named ‘TemplateDOC’ which will append a paragraph heading at last “11. Annex of Google Sheet Records.” at page 11 after appendPageBreak(). I need to set the page layout landscape so I can insert data range from a googlesheet named ‘logDATA’. The code goes like this but the result is null, please help to reach out the solution.

body.appendPageBreak();
body.appendParagraph("n11. Annex of Google Sheet Records.");
var paragraphs = body.getParagraphs();
var pageCounter = 1;
var switchToLandscape = false;

for (var pLen = 0; pLen < paragraphs.length; pLen++){
    var paragraph = paragraphs[pLen];
    if(paragraph.getText() == "11. Annex of Google Sheet Records." ){
        switchToLandscape = true;
        break;
    }
}
if(switchToLandscape && paragraph.getType() == DocumentApp.ElementType.BODY_SECTION){
    pageCounter++;
}
if(pageCounter==11){
    var element = paragraph;
    var parent = element.getParent();

if(parent.getType()==DocumentApp.ElementType.BODY_SECTION){
    var attribute = {};
    attribute[DocumentApp.Attribute.PAGE_WIDTH]=792;
    attribute[DocumentApp.Attribute.PAGE_HEIGHT]=612;
    parent.setAttributes(attribute);
}