Safari extension - how to use the setContextEventUserInfo method - safari-extension

Question

I am building a Safari extension.
On the manual, at the page about "Adding Contextual Menu Items", at the paragraph "Adding Contextual Menu Items Programmatically", it says:
You can add menu items to the contextual menu by responding to the
extension version of the "contextmenu" event in your global page or an
extension bar. If you stored information on the event by calling
setContextEventUserInfo() in your injected script, you can use that
information to help you decide what menu items to add.
Source:
https://developer.apple.com/library/archive/documentation/Tools/Conceptual/SafariExtensionGuide/AddingContextualMenuItems/AddingContextualMenuItems.html#//apple_ref/doc/uid/TP40009977-CH4-SW1
Now, I have this code on my injected script (as I am trying to pass the selected text to the background script):
function handleContextMenu(event) {
var htmlClip = getHtmlClip(event);
setContextEventUserInfo(htmlClip);
}
Unfortunately that generates this error:
ReferenceError: Can't find variable: setContextEventUserInfo
Unfortunately when I searched setContextEventUserInfo on Google, the only result was the page of the Safari manual!
Can please anybody explain to me how I am supposed to use the setContextEventUserInfo method?

Answer 1

This is what you need:
function handleContextMenu(event) {
var htmlClip = getHtmlClip(event);
safari.self.tab.setContextEventUserInfo(event, htmlClip);
}