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.

def get_or_add_video_media_part(self, video):
        """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.
        """
        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