code: def validate(self, data):
          
          video_id = self.context.get('video_id')
          video = Video.get_or_none(edx_video_id=video_id)
          if not video:
              raise serializers.ValidationError('Video "{video_id}" is not valid.'.format(video_id=video_id))
  
          data.update(video=video)
          return data
docs: Validates the transcript data.