def update(obj, values):
    """For given object, add all values in iterable values.

        Object and each value must be adaptable to IKeyReference.  Identical
        values (as determined by IKeyReference) are collapsed to a single
        instance (so, for instance, a set of [A, B, B, C, B] will be
        collapsed to a logical set of A, B, C).
        """
