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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 signOp(self, op: Dict, identifier: Identifier=None) -> Request: """ Signs the message if a signer is configured :param identifier: signing identifier; if not supplied the default for the wallet is used. :param op: Operation to be signed :return: a signed Request object """

        request = Request(operation=op,
                          protocolVersion=CURRENT_PROTOCOL_VERSION)
        return self.signRequest(request, identifier)