:param certificate_metadata:
        :param merkle_proof:
        :return:

def add_proof(self, certificate_metadata, merkle_proof):
        """
        :param certificate_metadata:
        :param merkle_proof:
        :return:
        """
        certificate_json = self._get_certificate_to_issue(certificate_metadata)
        certificate_json['signature'] = merkle_proof

        with open(certificate_metadata.blockchain_cert_file_name, 'w') as out_file:
            out_file.write(json.dumps(certificate_json))