input: 
  def reverse_double_linked_list(dlist: DoubleLinkedList) -> DoubleLinkedList:
      """Reverses a doubly linked list in-place.
      
      Example:
      dlist = DoubleLinkedList()
      dlist.append(1)
      dlist.append(2)
      dlist.append(3)
      reversed_dlist = reverse_double_linked_list(dlist)
      # After reversing, the list should be: head -> 3 -> 2 -> 1
      """
  
output:     current = dlist.head
      dlist.head = dlist.tail
      dlist.tail = current
      
      while current is not None:
          next_node = current.next
          current.next = current.prev
          current.prev = next_node
          current = next_node
      
      return dlist