def reduce_unique(items):
    """
    Reduce given list to a list of unique values and respecting original order
    base on first value occurences.

    Arguments:
        items (list): List of element to reduce.

    Returns:
        list: List of unique values.
    """
    used = set()
    return [x for x in items if x not in used and (used.add(x) or True)]