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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 decrypt_subtitle(self, subtitle):
 """Decrypt encrypted subtitle data in high level model object @param crunchyroll.models.Subtitle subtitle @return str """

        return self.decrypt(self._build_encryption_key(int(subtitle.id)),
            subtitle['iv'][0].text.decode('base64'),
            subtitle['data'][0].text.decode('base64'))