def certificateRequest(self, distinguishedName,
                           format=crypto.FILETYPE_ASN1,
                           digestAlgorithm='sha256'):
        """
        Create a certificate request signed with this key.

        @return: a string, formatted according to the 'format' argument.
        """
        return self.requestObject(distinguishedName, digestAlgorithm).dump(format)

        Create a certificate request signed with this key.

        @return: a string, formatted according to the 'format' argument.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/_sslverify.py