Add a client request to the transaction store's list of processed
        requests.

def addToProcessedTxns(self,
                           identifier: str,
                           txnId: str,
                           reply: Reply) -> None:
        """
        Add a client request to the transaction store's list of processed
        requests.
        """
        self.transactions[txnId] = reply
        if identifier not in self.processedRequests:
            self.processedRequests[identifier] = {}
        self.processedRequests[identifier][reply.reqId] = txnId