code: def init_app(self, app):
          
          if not hasattr(app, 'extensions'):
              app.extensions = {}
  
          service_name = app.config.get('GSSAPI_SERVICE_NAME', 'HTTP')
          hostname = app.config.get('GSSAPI_HOSTNAME', socket.getfqdn())
          principal = '{}@{}'.format(service_name, hostname)
          name = gssapi.Name(principal, gssapi.NameType.hostbased_service)
  
          app.extensions['gssapi'] = {
              'creds': gssapi.Credentials(name=name, usage='accept'),
          }
docs: Initialises the Negotiate extension for the given application.