def unique(sequence):
    """
    Return a list of unique items found in sequence. Preserve the original
    sequence order.
    For example:
    >>> unique([1, 5, 3, 5])
    [1, 5, 3]
    """
    deduped = []
    for item in sequence:
        if item not in deduped:
            deduped.append(item)
    return deduped