code: def _add_video_timing(self, pic):
          
          sld = self._spTree.xpath('/p:sld')[0]
          childTnLst = sld.get_or_add_childTnLst()
          childTnLst.add_video(pic.shape_id)
docs: Add a `p:video` element under `p:sld/p:timing`.
  
          The element will refer to the specified *pic* element by its shape
          id, and cause the video play controls to appear for that video.