How can I use "inpaint not masked" feature to add background to the image using diffusers?

I am trying to add background (outpainting) to the existing image. I see inpainting is available using diffusers: Inpainting but I don’t see the way to do outpainting. Any examples to achieve this will be really useful.
In Automatic1111 UI, I use “inpaint not masked” toggle to add outpainting to the image.
Thank you.

You could always invert the mask and then do inpainting.