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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 add_episode(self, text, text_format, title, author, summary=None, publish_date=None, synthesizer='watson', synth_args=None, sentence_break='. '):
 """ Add a new episode to the podcast. :param text: See :meth:`Episode`. :param text_format: See :meth:`Episode`. :param title: See :meth:`Episode`. :param author: See :meth:`Episode`. :param summary: See :meth:`Episode`. :param publish_date: See :meth:`Episode`. :param synthesizer: See :meth:`typecaster.utils.text_to_speech`. :param synth_args: See :meth:`typecaster.utils.text_to_speech`. :param sentence_break: See :meth:`typecaster.utils.text_to_speech`. """

        if title in self.episodes:
            raise ValueError('"' + title + '" already exists as an episode title.')

        link = self.output_path + '/' + title.replace(' ', '_').lower() + '.mp3'
        episode_text = convert_to_ssml(text, text_format)
        new_episode = Episode(episode_text, text_format, title, author, link, summary, publish_date, synthesizer, synth_args, sentence_break)

        self.episodes[title] = new_episode