def pair_window(iterable):
    """
    A more simple version of `window` for size=2.

    >>> list(window([11, 22, 33, 44]))
    [(11, 22), (22, 33), (33, 44)]
    """
    iterable = iter(iterable)
    try:
        prev_value = next(iterable)
    except StopIteration:
        return
    for item in iterable:
        yield prev_value, item
        prev_value = item
