to get the child iterators. In addition, its :py:meth:`~.tee.aclose` method
    immediately closes all children, and it can be used in an ``async with`` context
    for the same effect.
    If ``iterable`` is an iterator and read elsewhere, ``tee`` will *not*
    provide these items. Also, ``tee`` must internally buffer each item until the
    last iterator has yielded it; if the most and least advanced iterator differ
    by most data, using a :py:class:`list` is more efficient (but not lazy).
    If the underlying iterable is concurrency safe (``anext`` may be awaited
    concurrently) the resulting iterators are concurrency safe as well. Otherwise,
    the iterators are safe if there is only ever one single "most advanced" iterator.
    To enforce sequential use of ``anext``, provide a ``lock``
    - e.g. an :py:class:`asyncio.Lock` instance in an :py:mod:`asyncio` application -
    and access is automatically synchronised.
    """
[docs]    def __init__(
        self,
        iterable: AsyncIterator[T],
        n: int = 2,
        *,
        lock: Optional[AsyncContextManager[Any]] = None,
    ):
        self._iterator = iterable.__aiter__()  # before 3.10 aiter() doesn't exist
        self._buffers: List[Deque[T]] = [deque() for _ in range(n)]
        self._children = tuple(
            tee_peer(
                iterator=self._iterator,
                buffer=buffer,
                peers=self._buffers,
                lock=lock if lock is not None else NoLock(),
            )
            for buffer in self._buffers
        )
    def __len__(self) -> int: