def popleft(self, blocking = False, timeout = -1):
        if len(self) == 0 and blocking:
            self.channel.receive(timeout)
        return collections.deque.popleft(self)
Pop the first item from the start of the queue. If *blocking* is True, the caller will block for *timeout* seconds until an item 
dataset/ETHPy150Open concurrence/concurrence/lib/concurrence/core.py/Deque.popleft