Office Script; Excel online; Pivot Table; DataHierarchy field title

Question

I would like to change the title for a Pivot Table DataHierarchy field. I cannot find any documentation. Specifically, I'd like to change the field name from "Sum of aDate" to "aDate" I'm using Office Script/Java Script. I tried recording the task but the script uses hard coded reference

/*function main(workbook: ExcelScript.Workbook) {
	let selectedSheet = workbook.getActiveWorksheet();
	// Set range H9 on selectedSheet
	selectedSheet.getRange("H9").setValue(" 25Jul22");
}*/

thank you

Jenny