If this script is attached your AnimationPlayer then it doesn’t have a child so $AnimationPlayer doesn’t work, instead you could use self.play or just play.
You declare the function Eyelids but I do not know if you ever use it, maybe you mean to use the _input function which is called automatically for every input event
func _input(event: InputEvent) -> void:
if event is InputEventKey:
if event.keycode == KEY_SPACE:
if event.pressed:
play("Eyelids")
else:
play_backwards("Eyelids")
Make sure to paste code instead of screen shots