It's probably a dumb mistake that I'm making but I can't seem to get it to work, I'm simply trying to get the selected resolution option...

Here's the code I'm using.
onready var Resolution_Option = get_node("SettingsPopUp/CenterContainer/VBoxContainer/Resolution_Option")
func _on_Resolution_Option_item_selected(ID):
var Resolution = Resolution_Option.get_selected_metadata()
print(Resolution)
And it prints "Null"
I've also tried...
func _on_Resolution_Option_item_selected(ID):
var Resolution = Resolution_Option.get_item_metadata(ID)
print(Resolution)
Also prints "Null".