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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 getProvStack(self, iden: bytes):
        '''
        Returns the provenance stack given the iden to it
        '''
        retn = self.slab.get(iden, db=self.db)
        if retn is None:
            return None

        return s_msgpack.un(retn)