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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 signmessage(self, address, message):
 """Sign a message with the private key of an address. Cryptographically signs a message using ECDSA. Since this requires an address's private key, the wallet must be unlocked first. Args: address (str):
 address used to sign the message message (str):
 plaintext message to which apply the signature Returns: str: ECDSA signature over the message """

        signature = self.rpc.call("signmessage", address, message)
        self.logger.debug("Signature: %s" % signature)
        return signature