[SOLVED] hideItem not working as expected

Hi,

with this code

$master = $pageObject->getMasterRecord();

if ($master["Kurzname"] != Null or $master["Kurzname"] !="" )
	{
		$pageObject->hideItem("inlineAdd12");
		$pageObject->hideItem("addButton12");
		$pageObject->hideItem("update_selected12");
		$pageObject->hideItem("delete_selected12");
	}

in BeforeDisplay event I want to hide some buttons, if the list is shown as detail list of a specific table which has the field "Kurzname".

Should work regarding to documentation:
https://xlinesoft.com/phprunner/docs/hideitem.htm

But all I get is

Fatal error: Call to undefined method ListPage_DPInline::hideItem()

Working with 9.8 still.

Is there a bug? An error in documentation or am I doing something wrong?