code: def __frontend_limit_descriptor(self, api_info):
      
      if api_info.frontend_limits is None:
        return None
  
      descriptor = {}
      for propname, descname in (('unregistered_user_qps', 'unregisteredUserQps'),
                                 ('unregistered_qps', 'unregisteredQps'),
                                 ('unregistered_daily', 'unregisteredDaily')):
        if getattr(api_info.frontend_limits, propname) is not None:
          descriptor[descname] = getattr(api_info.frontend_limits, propname)
  
      rules = self.__frontend_limit_rules_descriptor(api_info)
      if rules:
        descriptor['rules'] = rules
  
      return descriptor
docs: Builds a frontend limit descriptor from API info.
  
      Args:
        api_info: An _ApiInfo object.
  
      Returns:
        A dictionary with frontend limit information.