[Python] PyCharm couldn't find a pre-installed module os but can still use it

I've using Pycharm for a while now. And recently I noticed that the import os line is highlighted in red with an error message of No module named os. (Using Python 3.8.4)



But when launching the script(Via PyCharm) it's importing it without any errors. The exact same thing is also happening with a module named webbrowser.

Why does it say this? And how do I fix this?

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