Google Apps Script or other Google Workspace email volume statistics solution with delegated accounts

Google Workspace

Need statistics of delegates who operate on the main account sending correspondence from it. Info is contained in the X-Google-Sender-Delegation headers and you can get to this most easily through Apps Script and, for example, export to sheets (which is enough for us, we do not need miracles here). The current contractor has fallen and the "work" is unfinished - but the concept was probably good.

This, of course, is to work subscription-free and within the google account - no external server, service, etc.

For those interested, I can send the code from the apps script which is currently (as I say - it works only as a concept and not an effective solution ;-)