def METHOD_NAME(self, message: bytes) -> bytes:
    """
    sign a message
    :param message: as bytes
    :return: signature: as bytes
    """
    if not self.signer:
        raise Exception("Signer not initialized!")
    if not self.signer.can_sign():
        raise Exception("unable to sign - signer not initialized?")
    return self.signer.METHOD_NAME(SHA256.new(message))