code: def next(self):
          
          smallest = None
          for key in self.queue.keys():
              if self.queue[key]['status'] == 'queued':
                  if smallest is None or key < smallest:
                      smallest = key
          return smallest
docs: Get the next processable item of the queue.
  
          A processable item is supposed to have the status `queued`.
  
          Returns:
              None : If no key is found.
              Int: If a valid entry is found.