Can't get Results of Ad in Business Manager through Marketing API

I use facebook business SDK to get data from facebook business manager by Python. I can get almost all fields using get_insights method, but I can't get Results field. And I don't see it in the documentation.

params_ads={'time_range': {'since': '2021-03-01', 'until': '2021-03-23'},'level': 'ad', 'limit': '20000'}
fields_ads = [AdsInsights.Field.account_id,
           AdsInsights.Field.account_name,
           AdsInsights.Field.ad_id,
           AdsInsights.Field.ad_name,
           AdsInsights.Field.adset_id,
           AdsInsights.Field.adset_name,
           AdsInsights.Field.campaign_id,
           AdsInsights.Field.campaign_name,
           AdsInsights.Field.spend,
           AdsInsights.Field.impressions,
           AdsInsights.Field.clicks,
           AdsInsights.Field.outbound_clicks,
        ]

ads = my_account.get_insights(params=params_ads, fields=fields_ads)