Employee Information Report

In HR-> Reports -> Employee Information, I want to know that what exactly part of code is running in order to display this report.
Because there is only json file, from where json file(columns, doctype) are retrieved and how these json data are executed in python file?

Since this is a straght-forward one table query, the fields / columns are enough definition. This is executed in reportview.js

Thanks for your reply

Regards,
Navera Arifi