How to make .py change work under production mode?

ERPNext V12.9.0 with production mode.
No matter how to change the .py file, when refresh browser, nothing happen, even though delete the file.
I wonder if there is cache mechanism under production mode?

sorry, i am new to ERPNext, the reason is gunicorn work mode.
got solution, restart gunicorn or add --reload option to supervisor conf.