code: def execute_pool_txns(self, three_pc_batch) -> List:
          
          committed_txns = self.default_executer(three_pc_batch)
          for txn in committed_txns:
              self.poolManager.onPoolMembershipChange(txn)
          return committed_txns
docs: 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