'If I am being sent back to where I came from, serialize as a local backreference.'

def jellyFor(self, jellier):

    if jellier.invoker:
        assert (self.broker == jellier.invoker), "Can't    send    references    to    brokers    other    than    their    own."
        return ('local', self.luid)
    else:
        return ('unpersistable', 'References    cannot    be    serialized')
