code: def _get_video(edx_video_id):
      
      try:
          return Video.objects.prefetch_related("encoded_videos", "courses").get(edx_video_id=edx_video_id)
      except Video.DoesNotExist:
          error_message = u"Video not found for edx_video_id: {0}".format(edx_video_id)
          raise ValVideoNotFoundError(error_message)
      except Exception:
          error_message = u"Could not get edx_video_id: {0}".format(edx_video_id)
          logger.exception(error_message)
          raise ValInternalError(error_message)
docs: Get a Video instance, prefetching encoded video and course information.
  
      Raises ValVideoNotFoundError if the video cannot be retrieved.