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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 _get_hash(self):
 """ Create hash of the class. Hash should be unique for given ebook, so ISBN is main component of the hash if provided. Returns: str: Hash. """

        if self.optionals and self.optionals.ISBN:
            isbn = self.optionals.ISBN.replace("-", "")

            if len(isbn) <= 10:
                return "97880" + isbn

            return isbn

        if self.optionals and self.optionals.EAN:
            return self.optionals.EAN

        return self.title + ",".join(map(lambda x: x.name, self.authors))