def SignMessage(self, message, script_hash):
        """
        Sign a message with a specified script_hash.

        Args:
            message (str): a hex encoded message to sign
            script_hash (UInt160): a bytearray (len 20).

        Returns:
            str: the signed message
        """

        keypair = self.GetKeyByScriptHash(script_hash)
        prikey = bytes(keypair.PrivateKey)
        res = Crypto.Default().Sign(message, prikey)
        return res, keypair.PublicKey
Sign a message with a specified script_hash.

        Args:
            message (str): a hex encoded message to sign
            script_hash (UInt160): a bytearray (len 20).

        Returns:
            str: the signed message