code: def get_login_url(self):
          
          params = {'service': self.service_url}
          if self.renew:
              params.update({'renew': 'true'})
  
          params.update(self.extra_login_params)
          url = urllib_parse.urljoin(self.server_url, 'login')
          query = urllib_parse.urlencode(params)
          return url + '?' + query
docs: Generates CAS login URL