Check if entity is despawned

How do I check if entity is despAwned

 

PHP:

if ($entity->isClosed() || $entity->isFlaggedForDespawn()) {

}

 

PHP:

 if($entity->isFlaggedForDespawn()) {

}

I don't know about Entities that have already been despawned. I think the object would be closed after that, meaning maybe

PHP:

 if($entity instanceof Entity) 

might work? I am not sure on that though.