Return unique list of items preserving order.

    >>> uniqued([3, 2, 1, 3, 2, 1, 0])
    [3, 2, 1, 0]

def uniqued(iterable):
    """Return unique list of items preserving order.

    >>> uniqued([3, 2, 1, 3, 2, 1, 0])
    [3, 2, 1, 0]
    """
    seen = set()
    add = seen.add
    return [i for i in iterable if i not in seen and not add(i)]