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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 expand(self, new_size):
 """ expand the LUN to a new size :param new_size: new size in bytes. :return: the old size """

        ret = self.size_total
        resp = self.modify(size=new_size)
        resp.raise_if_err()
        return ret