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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 execute_pool_txns(self, three_pc_batch) -> List: """ Execute a transaction that involves consensus pool management, like adding a node, client or a steward. :param ppTime: PrePrepare request time :param reqs_keys: requests keys to be committed """

        committed_txns = self.default_executer(three_pc_batch)
        for txn in committed_txns:
            self.poolManager.onPoolMembershipChange(txn)
        return committed_txns