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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def validate(self, data):
 """ Validates the transcript 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