def assert_is_subclass(subcls, cls, msg=''):
 assert issubclass(subcls, cls), ('%s is not a subclass of %s\n%s' % (_safe_cls_name(subcls), _safe_cls_name(cls), msg))

def assert_is_subclass ( subcls , cls , msg = '' ) : assert issubclass ( subcls , cls ) , ( '%s is not a subclass of %s\n%s' % ( _safe_cls_name ( subcls ) , _safe_cls_name ( cls ) , msg ) )
assert that subcls is a subclass of cls .