old_contents: from __future__ import absolute_import
  from __future__ import print_function
  from __future__ import division
  
  
  class Queue(object):
      """Queue class."""
      def __init__(self):
          self.items = []
  
      def is_empty(self):
          return self.items == []
  
      def enqueue(self, item):
          self.items.insert(0, item)
  
      def dequeue(self):
          return self.items.pop()
      
      def size(self):
          return len(self.items)
  
  
  def main():
      queue = Queue()
  
      queue.is_empty()
  
      queue.enqueue('dog')
      queue.enqueue(4)
      queue.enqueue(8.4)
  
      print('Queue size: {}'.format(queue.size()))
  
      print('Dequeue: {}'.format(queue.dequeue()))
      print('Queue size: {}'.format(queue.size()))
  
  if __name__ == '__main__':
      main()
  
new_contents: from __future__ import absolute_import
  from __future__ import print_function
  from __future__ import division
  
  
  class Queue(object):
      """Queue class."""
      def __init__(self):
          self.items = []
  
      def is_empty(self):
          return self.items == []
  
      def enqueue(self, item):
          self.items.insert(0, item)
  
      def dequeue(self):
          return self.items.pop()
      
      def size(self):
          return len(self.items)
  
  
  def main():
      queue = Queue()
  
      print('Is empty: {}'.format(queue.is_empty()))
  
      print('Enqueue "dog", 4 & 8.4')
      queue.enqueue('dog')
      queue.enqueue(4)
      queue.enqueue(8.4)
      print('Is empty: {}'.format(queue.is_empty()))
  
      print('Queue size: {}'.format(queue.size()))
  
      print('Dequeue: {}'.format(queue.dequeue()))
      print('Is empty: {}'.format(queue.is_empty()))
      print('Queue size: {}'.format(queue.size()))
  
  if __name__ == '__main__':
      main()
  
subject: Revise main() for testing