def multiple_signatures(self, statement, to_sign, key=None, key_file=None,
                            passphrase=None):
        for (item, sid, id_attr) in to_sign:
            if not sid:
                if not item.id:
                    sid = item.id = sid()
                else:
                    sid = item.id

            if not item.signature:
                item.signature = pre_signature_part(sid, self.cert_file)

            statement = self.sign_statement(statement, class_name(item),
                                            key=key, key_file=key_file,
                                            node_id=sid, id_attr=id_attr,
                                            passphrase=passphrase)
        return statement


# ===========================================================================
Sign multiple parts of a statement
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/pysaml2-2.4.0/src/saml2/sigver.py/SecurityContext.multiple_signatures