bad-mcs-classmethod-argument / C0204

Message emitted:

Metaclass class method %s should have %s as first argument

Description:

Used when a metaclass class method has a first argument named differently than the value specified in valid-metaclass-classmethod-first-arg option (default to "mcs"), recommended to easily differentiate them from regular instance methods.

Problematic code:

class Meta(type):
    @classmethod
    def foo(some):  # [bad-mcs-classmethod-argument]
        pass

Correct code:

class Meta(type):
    @classmethod
    def foo(mcs):
        pass

Created by the classes checker.