code: def init_authentication_method(self, request, authn_method,
                                     http_args=None, **kwargs):
          
          if http_args is None:
              http_args = {}
  
          if authn_method:
              logger.debug('Client authn method: {}'.format(authn_method))
              return self.client_authn_factory(authn_method).construct(
                  request, self, http_args=http_args, **kwargs)
          else:
              return http_args
docs: Will run the proper client authentication method.
          Each such method will place the necessary information in the necessary
          place. A method may modify the request.
  
          :param request: The request, a Message class instance
          :param authn_method: Client authentication method
          :param http_args: HTTP header arguments
          :param kwargs: Extra keyword arguments
          :return: Extended set of HTTP header arguments