How to use python to collect the launching time of

I try to use the selenium package to collect the startup time length of my binder repository but I have difficulty in getting the ending time point(Jupiter notebook shows up).

For the ending timepoint, I tried several ways but none of them provide me with the right time length:

driver.execute_script( “return window.performance.timing.domComplete”)
driver.execute_script( “return window.performance.timing.LoadEventEnd”)
driver.execute_script( “return window.performance.timing.RedirectEnd”)

Is there any way to get the launching time for a repository?