||The tween instance|
bool) If the tween has been initialized
Returns true if a given tween is initted. A tween is considered initted,
when all the variables and current values are captured from the target instance.
The values for a tween are captured on the very first step that the tween is
rendered. For example, if you create a tween with
10, the tween
will be initialized on the very first frame after the 10 seconds delay.
tween_from tweens are initialized on the same frame that are created.
Normally, you don't use this value for anything. Only for advanced debug purposes.