Try to fix NoneType
Because mypy doesn't like the type alias.
@@ -11,7 +11,7 @@ from ..interpreterbase.decorators import KwargInfo, ContainerTypeInfo
from ..mesonlib import FileMode, MachineChoice
# Helper definition for type checks that are `Optional[T]`
-NoneType = type(None)
+NoneType: T.Type[None] = type(None)
def in_set_validator(choices: T.Set[str]) -> T.Callable[[str], T.Optional[str]]:
