code: def construct(self, request=None, service=None, http_args=None,
                    **kwargs):
          
  
          if service.service_name == 'refresh_token':
              _acc_token = find_token(request, 'refresh_token', service, **kwargs)
          else:
              _acc_token = find_token(request, 'access_token', service, **kwargs)
  
          if not _acc_token:
              raise KeyError('No access or refresh token available')
  
          # The authorization value starts with 'Bearer' when bearer tokens
          # are used
          _bearer = "Bearer {}".format(_acc_token)
  
          # Add 'Authorization' to the headers
          if http_args is None:
              http_args = {"headers": {}}
              http_args["headers"]["Authorization"] = _bearer
          else:
              try:
                  http_args["headers"]["Authorization"] = _bearer
              except KeyError:
                  http_args["headers"] = {"Authorization": _bearer}
  
          return http_args
docs: Constructing the Authorization header. The value of
          the Authorization header is "Bearer <access_token>".
  
          :param request: Request class instance
          :param service: Service
          :param http_args: HTTP header arguments
          :param kwargs: extra keyword arguments
          :return: