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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 resolve_one(self, correlation_id, key):
 """ Resolves a single connection parameters by its key. :param correlation_id: (optional) transaction id to trace execution through call chain. :param key: a key to uniquely identify the connection. :return: a resolved connection. """

        connection = None
        for item in self._items:
            if item.key == key and item.connection != None:
                connection = item.connection
                break
        return connection