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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 files_before(self, *, bundle: str=None, tags: List[str]=None, before: str=None) -> models.File: """Fetch files before date from store"""

        query = self.files(tags=tags, bundle=bundle)
        if before:
            before_dt = parse_date(before)
            query = query.join(models.Version).filter(models.Version.created_at < before_dt)

        return query