It's possible to stop the debugger from stepping into library functions when you press Step into F7 bu going to File > Settings > Build, Execution, Deployment > Debugger > Stepping > Python and checking the option Do not step into library scripts.
(One alternative could also be using Step into my code Alt + Shift + F7).
As shown in the screenshot.

The following is a code example using only standard library that can be copied for testing
import os
def my_function():
return 2
my_str = str(os.path.join(os.getcwd(), str(my_function())))
This screenshot shows using Step into F7 having Do not step into library scripts unchecked and Always do smart step into checked.

Notice the 3 setting options are interconnected, if you choose Do not step into library scripts together with Always do smart step into the IDE will still give you a choice to step into the library function. If you uncheck the later option the above example will automatically step into your function.