//iterator() creates a new Iterator over this list. It will //initially be referring to the first value in the list, unless the //list is empty, in which case it will be considered both "past start" //and "past end".

template typename DoublyLinkedList::Iterator DoublyLinkedList::iterator() { //return iterator(head); }

//constIterator() creates a new ConstIterator over this list. It will //initially be referring to the first value in the list, unless the //list is empty, in which case it will be considered both "past start" //and "past end".

template typename DoublyLinkedList::ConstIterator DoublyLinkedList::constIterator() const { //return constIterator(head); }

//Initializes a newly-constructed IteratorBase to operate on //the given list. It will initially be referring to the first //value in the list, unless the list is empty, in which case //it will be considered to be both "past start" and "past end". //template DoublyLinkedList::IteratorBase::IteratorBase(const DoublyLinkedList& list) noexcept { }

Need implementation on those 3 functions, show all the steps with explanation in c++