The provider method

    SomeProvider.provide_a() -> SomeBaseClass

provides for

    SomeProvider.a = Resource(SomeConcreteClass, ResourceKind.OVERRIDE)

But the method's return type annotation 'SomeBaseClass' is not compatible with
'SomeConcreteClass'
So the return type must be compatible with 'SomeConcreteClass'

SomeProvider: "src/seamful/provider/test_provider.py"
