How to know the storage or logical size of a flex cluster from trigger

[touhidurrr (Md. Touhidur Rahman)]

I was to implement an auto cleanup trigger. However, I am not being able to find any way to see information like logical size or storage size from inside triggers. None of the methods in the previous question works. Sauce:

https://www.mongodb.com/community/forums/t/how-to-know-disk-used-from-a-trigger/

So, how can I do this? I am only getting empty values using the previously working method.