How to send more labels in the "context" of InteractiveAnnotating"

In the "label-studio-ml-backend/label_studio_ml/examples/tesseract/tesseract.py", it uses "context = kwargs.get('context')" to get the annotation actions performed in Label Studio, such as only one "rectangle" and one "labels". and it will return "textarea".
But the context only include one image area.
Now, I need annotations of **other image areas** to **link the area automatically**(create "relation" annotation).
Concretely, when I choice many image areas or draw a rectangle including many image areas, it can create "relation" annotations according to specific rules(e.g. from left to right, from top to down).

How do I implement this functionality with the "InteractiveAnnotating"?
Thanks.