如何使用Facebook Insight API过滤一个指定操作的值？

Question

如Ad Insights doc所述：

我们可以使用参数filtering来过滤指定的广告见解，例如：

https://graph.facebook.com/<VERSION>/act_ID/insights?access_token=token&fields=ad_id,impressions&date_preset=lifetime&level=ad&filtering=[{"field":"ad.effective_status","operator":"IN","value":["DELETED"]}]

# filtering=[{"field":"ad.effective_status","operator":"IN","value":["DELETED"]}]

过滤已删除的有效状态广告数据。

现在我需要过滤指定的见解数据，例如，其action_type offsite_conversion.fb_pixel_add_to_cart的值小于5的数据， 如何使此过滤有效？

# tried 

filtering=[{"field":"actions.offsite_conversion.fb_pixel_add_to_cart",
"operator":"LESS_THAN",
"value":5}]

# but failed

   "actions": [
       {
          "action_type": "offsite_conversion.fb_pixel_add_to_cart",
          "value": "5"
        },