You may specify output_segmentation=True in the forward of GroupViTModel to get the segmentation logits of input texts. 

Resources
A list of official Hugging Face and community (indicated by 🌎) resources to help you get started with GroupViT.

The quickest way to get started with GroupViT is by checking the example notebooks (which showcase zero-shot segmentation inference).
One can also check out the HuggingFace Spaces demo to play with GroupViT.