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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 transaction(self, txn):
 """Txn processes multiple requests in a single transaction. A txn request increments the revision of the key-value store and generates events with the same revision for every completed request. It is not allowed to modify the same key several times within one txn. :param txn: :return: """

        return self.post(self.get_url("/kv/txn"),
                         data=json.dumps(txn))