def unique(iterable):
    """Return an iterable of the same type which contains unique items.

    This function assumes that:
    type(iterable)(list(iterable)) == iterable
    which is true for tuples, lists and deques (but not for strings)

    >>> unique([1, 2, 3, 1, 2, 3, 4, 2, 3, 4, 1, 1, 2])
    [1, 2, 3, 4]
    >>> unique(('w', 't', 't', 'f', 't', 'w'))
    ('w', 't', 'f')
    """
    already_seen = []
    for item in iterable:
        if item not in already_seen:
            already_seen.append(item)
    return type(iterable)(already_seen)