Python chunks function with overlaps

chunks.py

def skip(iterator, n):
    """
    skip n items in iterator

    from itertools recipes:
    https://docs.python.org/3/library/itertools.html#itertools-recipes
    (see "consume")
    :param iterator: iterator to skip
    :param n: items to skip
    :return: iterator with n items skipped
    """

    # Use functions that consume iterators at C speed.
    if n is None:
        # feed the entire iterator into a zero-length deque
        collections.deque(iterator, maxlen=0)
    else:
        # advance to the empty slice starting at position n
        next(islice(iterator, n, n), None)
    return iterator


def chunks(iterable, n, step=None, trim=False):
    """
    create a generator for chunks from a general iterable
    :param iterable: any iterable item
    :param n: chunk size
    :param int step: step size
    :param int trim: trim trailing results smaller than n
    :return: generator of n-chunks
    """
    its = tee(iter(iterable), n)

    # advance iterators to create iterator window
    its = starmap(skip, map(reversed, enumerate(its)))

    # apply step to all iterators
    its = (islice(it, 0, None, step or n) for it in its)

    # zip iterators to create all chunks
    windows = zip_longest(*its, fillvalue=_NOT_SET)

    # remove _NOT_SETS from chunks
    windows = (tuple(v for v in w if v is not _NOT_SET) if
               w[-1] is _NOT_SET else w for w in windows)

    # filter results smaller than n
    if trim:
        windows = (w for w in windows if len(w) == n)

    yield from windows