code: def login_service_description(self):
          
          desc = super(IIIFAuthClickthrough, self).login_service_description()
          desc['confirmLabel'] = self.confirm_label
          return desc
docs: Clickthrough login service description.
  
          The login service description _MUST_ include the token service
          description. Additionally, for a clickthroudh loginThe authentication pattern is indicated via the
          profile URI which is built using self.auth_pattern.