これです。 __init__ の引数に '*' (アスタリスク) が1個、ポツンとありますよね。 class Queue: """A queue, useful for coordinating producer and consumer coroutines. ... """ def __init__(self, maxsize=0, *, loop=None): if loop is None: self._loop = events.get_event_loop() else: self._loop = loop self._maxsize = maxsize # Futures. self._getters = collections.deque() # Futures. self._putters = collections.deque() self._unfinished_t