code: def __frontend_limit_rules_descriptor(self, api_info):
      
      if not api_info.frontend_limits.rules:
        return None
  
      rules = []
      for rule in api_info.frontend_limits.rules:
        descriptor = {}
        for propname, descname in (('match', 'match'),
                                   ('qps', 'qps'),
                                   ('user_qps', 'userQps'),
                                   ('daily', 'daily'),
                                   ('analytics_id', 'analyticsId')):
          if getattr(rule, propname) is not None:
            descriptor[descname] = getattr(rule, propname)
        if descriptor:
          rules.append(descriptor)
  
      return rules
docs: Builds a frontend limit rules descriptor from API info.
  
      Args:
        api_info: An _ApiInfo object.
  
      Returns:
        A list of dictionaries with frontend limit rules information.