def rename_slide_parts(self, rIds):
        """
        Assign incrementing partnames like ``/ppt/slides/slide9.xml`` to the
        slide parts identified by *rIds*, in the order their id appears in
        that sequence. The name portion is always ``slide``. The number part
        forms a continuous sequence starting at 1 (e.g. 1, 2, ... 10, ...).
        The extension is always ``.xml``.
        """
        for idx, rId in enumerate(rIds):
            slide_part = self.related_parts[rId]
            slide_part.partname = PackURI(
                '/ppt/slides/slide%d.xml' % (idx+1)
            )