# The C code is way more low-level than this, as it implements
            # all methods of the iterator protocol. In this implementation
            # we're relying on higher-level coroutine concepts, but that's
            # exactly what we want -- crosstest pure-Python high-level
            # implementation and low-level C anext() iterators.
            return await __anext__(iterator)
        except StopAsyncIteration:
            return default
    return anext_impl()
[docs]class NoLock:
    """Dummy lock that provides the proper interface but no protection"""
    async def __aenter__(self) -> None:
        pass
    async def __aexit__(self, exc_type: Any, exc_val: Any, exc_tb: Any) -> bool:
        return False
[docs]async def tee_peer(
    iterator: AsyncIterator[T],
    # the buffer specific to this peer
    buffer: Deque[T],
    # the buffers of all peers, including our own
    peers: List[Deque[T]],
    lock: AsyncContextManager[Any],
) -> AsyncGenerator[T, None]:
    """An individual iterator of a :py:func:`~.tee`"""
    try:
        while True:
            if not buffer:
                async with lock:
                    # Another peer produced an item while we were waiting for the lock.
                    # Proceed with the next loop iteration to yield the item.
                    if buffer:
                        continue
                    try:
                        item = await iterator.__anext__()
                    except StopAsyncIteration:
                        break
                    else:
                        # Append to all buffers, including our own. We'll fetch our
                        # item from the buffer again, instead of yielding it directly.
                        # This ensures the proper item ordering if any of our peers