corner case: when __module__ is __main__ (i.e. the callable is
defined in the same module as __main__). In this case,
f.__module__ returns "__main__" instead of the file that it is
corner case: when __module__ is __main__ (i.e. the callable is
defined in the same module as __main__). In this case,
f.__module__ returns "__main__" instead of the file that it is