IOS and mutable-content

Due to the documentation : 
https://developer.apple.com/library/content/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/ModifyingNotifications.html

I should Include the mutable-content key with a value of 1. 
But, i cant because in AppleNotification.php the supportedOptions are badge, sound and content-available.

Could you had in this supported options 'mutable-content' ?