Consider the following example:

```
from abc import ABCMeta, ABC

class MetaclassMixin(ABC):
    pass 

class Meta(MetaclassMixin, ABCMeta):
    pass

class A(metaclass=Meta):
    pass

```

Then the call `isinstance(A, Meta)` returns `True` but `isinstance(1, Meta)` raises 

 >>> TypeError: __subclasscheck__() missing 1 required positional argument: 'subclass'

Checked on 3.6.9, 3.8.0 & 3.8.8