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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 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