From the commit message, to fix running the introspection tests when Python 3.8.x or later is being used:
...when we are using Python 3.8.x or later. Python 3.8.x or later on Windows require one to call
os.add_dll_directory() on every directory that contains dependent non-system DLLs of a module that are not bundled/installed with the module.
Since we are very likely running programs that rely on dependent items in
%PATH%, make things easier for people by calling os.add_dll_directory() on all the valid paths in
api.py, so that the test will run successfully on Windows with Python 3.8.x or later.
With blessings, thank you!