Python:Error GoogleAdsServerFault:[UserListError.USER\u LIST\u MUTATE\u不受支持

我正在尝试将adwords帐户中列表的成员寿命更新为30天。 下面是我的代码片段

 adwords_client = adwords.AdWordsClient.LoadFromString('my credentials')
 adwords_client.SetClientCustomerId('my client id')
 user_list_service = adwords_client.GetService('AdwordsUserListService', 'v201809')

 user_list = {
      'id' : 'my list id',
      'membershipLifeSpan': 30
              }

  # Create an operation to add the user list.
 operations = [{
      'operator': 'SET',
      'operand': user_list
  }]

 result = user_list_service.mutate(operations)

下面是错误

GoogleAdsServerFault: [UserListError.USER_LIST_MUTATE_NOT_SUPPORTED @ operations[0].operand]