code: def get_or_add_video_media_part(self, video):
          
          media_part = self._package.get_or_add_media_part(video)
          media_rId = self.relate_to(media_part, RT.MEDIA)
          video_rId = self.relate_to(media_part, RT.VIDEO)
          return media_rId, video_rId
docs: Return rIds for media and video relationships to media part.
  
          A new |MediaPart| object is created if it does not already exist
          (such as would occur if the same video appeared more than once in
           a presentation). Two relationships to the media part are created,
          one each with MEDIA and VIDEO relationship types. The need for two
          appears to be for legacy support for an earlier (pre-Office 2010)
          PowerPoint media embedding strategy.