code: def list_messages(self, queue, include_claimed=False, echo=False,
              marker=None, limit=None):
          
          return queue.list(include_claimed=include_claimed, echo=echo,
                  marker=marker, limit=limit)
docs: Returns a list of messages for the specified queue.
  
          By default only unclaimed messages are returned; if you want claimed
          messages included, pass `include_claimed=True`. Also, the requester's
          own messages are not returned by default; if you want them included,
          pass `echo=True`.
  
          The 'marker' and 'limit' parameters are used to control pagination of
          results. 'Marker' is the ID of the last message returned, while 'limit'
          controls the number of messages returned per reuqest (default=20).