code: def get_authn_header(self, request, authn_method, **kwargs):
          
          headers = {}
          # If I should deal with client authentication
          if authn_method:
              h_arg = self.init_authentication_method(request, authn_method,
                                                      **kwargs)
              try:
                  headers = h_arg['headers']
              except KeyError:
                  pass
  
          return headers
docs: Construct an authorization specification to be sent in the
          HTTP header.
  
          :param request: The service request
          :param authn_method: Which authentication/authorization method to use
          :param kwargs: Extra keyword arguments
          :return: A set of keyword arguments to be sent in the HTTP header.