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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_subs_by_uid(self, uid):
 """ Find all subject identifiers that is connected to a User ID. :param uid: A User ID :return: A set of subject identifiers """

        res = set()
        for sid in self.get('uid2sid', uid):
            res |= set(self.get('sid2sub', sid))
        return res