code: def _create(self, common_name, public_key_algorithm='rsa',
              signature_algorithm='rsa_sha_512', key_length=2048,
              signing_ca=None):
          
          if signing_ca is None:
              signing_ca = VPNCertificateCA.objects.filter('Internal RSA').first()
          
          cert_auth = element_resolver(signing_ca)
          
          return ElementCreator(
              GatewayCertificate,
              exception=CertificateError,
              href=self.internal_gateway.get_relation('generate_certificate'),
              json={
                  'common_name': common_name,
                  'public_key_algorithm': public_key_algorithm,
                  'signature_algorithm': signature_algorithm,
                  'public_key_length': key_length,
                  'certificate_authority_href': cert_auth})
docs: Internal method called as a reference from the engine.vpn
          node