In which situation sys.modules["__main__"].__file__ is None?

[Diogo-Rossi]

I saw a pylance warning in a code, complaining about the types of sys.modules["__main__"].__file__.

By inspecting its type, I could see that the type is str | None.
I know that this attribute doesn't exist in some situations (Python REPL), but in which situation it is None?

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The line raising the warning is the following. Is this related to type None or is there some another problem?

os.path.abspath(sys.modules["__main__"].__file__)

Message: Type "str | None" is incompatible with constrained type variable "AnyStr"