Which XXX completes the insert$\_$after$()$ method in the Python LinkedList class for a

doubly$-$linked list?

def insert$\_$after$($self$,$ current$\_$node, new$\_$node$)$:

if self.head is None:

self.head $=$ new$\_$node

self.tail $=$ new$\_$node

elif current$\_$node is self.tail:

self.tail.next $=$ new$\_$node

new$\_$node.prev $=$ self.tail

self.tail $=$ new$\_$node

else:

successor$\_$node $=$ current$\_$node.next

new$\_$node.next $=$ successor$\_$node

new$\_$node.prev $=$ current$\_$node

current$\_$node.next $=$ new$\_$node

$xxx$

successor$\_$node.next $=$ new$\_$node

successor$\_$node.prev $=$ new$\_$node

current$\_$node.prev $=$ new$\_$node

current$\_$node.prev $=$ successor$\_$node