def METHOD_NAME(self):
    """
    Get the private as a string
    :returns: S_OK(PEM encoded PKey)
    """
    if not self.__valid:
        return S_ERROR(DErrno.ENOCERT)
    try:
        pkeyStr = self.__pkeyObj.as_pem(cipher=None, callback=M2Crypto.util.no_passphrase_callback).decode("ascii")
    except Exception as e:
        return S_ERROR(DErrno.EX509, f"Can't serialize pkey: {e}")
    return S_OK(pkeyStr)