def sign(self, message):
message = _helpers._to_bytes(message, encoding='<STR_LIT:utf-8>')<EOL>return PKCS1_v1_5.new(self._key).sign(SHA256.new(message))<EOL>
Signs a message.

        Args:
            message: string, Message to be signed.

        Returns:
            string, The signature of the message for the given key.