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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def diff(new, old):
 """ Compute the difference in items of two revisioned collections. If only `new' is specified, it is assumed it is not an update. If both are set, the removed items are returned first. Otherwise, the updated and edited ones are returned. :param set new: Set of new objects :param set old: Set of old objects :return: A tuple consisting of `(added, removed, is_update)`. :rtype: tuple """


    if old is not None:
        is_update = True

        removed = set(new.removed(old))
        updated = set(new.updated(old))
    else:
        is_update = False

        updated = new
        removed = set()

    return updated, removed, is_update