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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 iter_festival_countdown(countdown: Optional[int] = None, date_obj: MDate = None, lang: str = 'zh-Hans') -> FestivalCountdownIterable: """Return countdown of festivals. """

    factory = FestivalFactory(lang=lang)
    return factory.iter_festival_countdown(countdown, date_obj)