For the other 2 below u need to use the the function call_deferred.
So u are probably either trying to change a scene or reload the current since. It goes like
get_tree().reload_current_scene.call_deferred()
or get_tree().call_deferred("reload_current_scene").
Although there is a difference between reloading and changing scene. reloading a scene has no arguments so its fine like that. But for changing scene u need to add arguments into the parameters of the call function. Like
get_tree().change_current_scene_to_packed.call_deferred( The packed scene u want to load )
or get_tree().call_defered("change_current_scene_to_packed", The packed scene u want to load)
