Equivalent to `image.affine_mat = image.affine_mat @ func()`.

def affine(self, func:AffineFunc, *args, **kwargs)->'Image':
        "Equivalent to `image.affine_mat = image.affine_mat @ func()`."
        m = tensor(func(*args, **kwargs)).to(self.device)
        self.affine_mat = self.affine_mat @ m
        return self