@CalderH I searched for posts in this community forum that contain the text get_menu_item_value and found a post from Andreas. There, you'll see Andreas uses...
await callBTT("get_menu_item_value", {
... instead of this, as you do in your script...
await get_menu_item_value(
Your version of the script should work soon.
Unfortunately there's no mention of callBTT in the docs.