code: def _video_part_rIds(self):
          
          media_rId, video_rId = self._slide_part.get_or_add_video_media_part(
              self._video
          )
          return media_rId, video_rId
docs: 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.