input: 
  def print_linked_list_contents(linked_list):
      """Prints the contents of a given linked list.
      >>> node1 = Node(1)
      >>> node2 = Node(2)
      >>> node3 = Node(3)
      >>> linked_list = LinkedList()
      >>> linked_list.head = node1
      >>> node1.next = node2
      >>> node2.next = node3
      >>> print_linked_list_contents(linked_list)
      1
      2
      3
      """
      current_node = linked_list.head
      while current_node:
          print(current_node.data)
          current_node = current_node.next
  
output:     current_node = linked_list.head
      while current_node:
          print(current_node.data)
          current_node = current_node.next