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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 unpack_unsubscribe_rsp(cls, rsp_pb):
 """Unpack the un-subscribed response"""

        if rsp_pb.retType != RET_OK:
            return RET_ERROR, rsp_pb.retMsg, None

        return RET_OK, "", None