I too got this error. Incidentally, i typed __int__ instead of __init__.
I think, in many mistype cases the IDE i am using (IntelliJ) would have changed the color to the default set for Function definition. But, in my case __int__ being another dunder/magic method, color remained same as the one which IDE displays for __init__ (default Predefined item definition color), which took me some time in spotting the missing i.