old_contents: """Implementation of Queue."""
  
  from dll import DoublyLinkedList
  
  
  class Queue(object):
      """Class implementation of queue.
  
      1.  Enqueue: Add new head node.
      2.  Dequeue: Remove tail node.
      3.  Peek: Display tail node,
      4.  Size: Display queue length.
  
      """
  
      def __init__(self, iterable=None):
          """Instatiate Queue."""
          self.dll = DoublyLinkedList(iterable)
  
      def enqueue(self, contents):
          """Add new head node."""
          self.dll.push(contents)
  
      def dequeue(self):
          """Remove last node."""
          old_tail_node_contents = self.dll.shift()
          return old_tail_node_contents
  
      def peek(self):
          """Display but don't remove the contents of tail node."""
          try:
              return self.dll.tail_node.contents
          except AttributeError:
              return None
  
      def size(self):
          """Return Queue length."""
          return self.dll.length
new_contents: """Implementation of Queue."""
  
  from dll import DoublyLinkedList
  
  
  class Queue(object):
      """Class implementation of queue.
  
      1.  Enqueue: Add new head node.
      2.  Dequeue: Remove tail node.
      3.  Peek: Display tail node,
      4.  Size: Display queue length.
  
      """
  
      def __init__(self, iterable=None):
          """Instatiate Queue."""
          self.dll = DoublyLinkedList(iterable)
  
      def enqueue(self, contents):
          """Add new head node."""
          self.dll.push(contents)
  
      def dequeue(self):
          """Remove last node."""
          try:
              old_tail_node_contents = self.dll.shift()
              return old_tail_node_contents
          except IndexError:
              raise IndexError('Queue is already empty.')
  
      def peek(self):
          """Display but don't remove the contents of tail node."""
          try:
              return self.dll.tail_node.contents
          except AttributeError:
              return None
  
      def size(self):
          """Return Queue length."""
          return self.dll.length
  
subject: fix our dll