docs: 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