Class DoubleLinkerIterator returns the next value when using linkers of linked type lists.
Create an iterator starting at the given item.
The item to start from.
Get the current item and move on to the following one.
Optional
Not used, present to match the Iterator interface.
The current item, or done when there are no more.
Class DoubleLinkerIterator returns the next value when using linkers of linked type lists.