new_contents: class LinkedQueue:
      class _Node:
  
          __slots__ = '_element', '_next'
  
          def __init__(self, element):
              self._element = element
              self._next = next
  
      def __init__(self):
          self._head = None
          self._tail = None
          self._size = 0
  
      def __len__(self):
          return self._size
  
      def enqueue(self, e):
          node = self._Node(e)
          if self._size == 0:
              self._head = node
          else:
              self._tail._next = node
          self._tail = node
          self._size += 1
  
      def dequeue(self):
          node = self._head
          self._head = self._head._next
          if self._size == 0: self._tail = None
          self._size -= 1
          return node._element
  
  
              
          
          
subject: Add LinkedQueue