method_overridden() incorrect signature

[peterschutt]

In method_overridden(), the instance arg is typed as Model:

djangorestframework-stubs/rest_framework-stubs/relations.pyi

Line 9 in 466b1f5

def method_overridden(method_name: str, klass: type, instance: Model) -> bool: ...

However, the only time the func is called in drf source is in RelatedField.__init__() checking that get_queryset() is overridden:

if not method_overridden('get_queryset', RelatedField, self):

Perhaps instance should just be typed Any?

I'll be happy to PR when I get some time.