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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 save(self, obj):
 """ save an object :param obj: the object :return: the saved object """

        if obj not in self.session:
            self.session.add(obj)
        else:
            obj = self.session.merge(obj)
        self.session.flush()
        self.session.refresh(obj)
        return obj