Return the rIds for relationships to media part for video.

        This is where the media part and its relationships to the slide are
        actually created.

def _video_part_rIds(self):
        """Return the rIds for relationships to media part for video.

        This is where the media part and its relationships to the slide are
        actually created.
        """
        media_rId, video_rId = self._slide_part.get_or_add_video_media_part(
            self._video
        )
        return media_rId, video_rId