How to make Class instance in main.py available in another file?

I am having difficulty where I need to make the information available in a class that is instantiated in main.py in another file. The best way to describe what I am trying to do can be seen in the flow diagram below:

The issue as you can imagine is with circular dependency. Is there a way to create an interface between schema.py and main.py so that I can pass class information?

Thank you for your time and any help you can offer!

Cheers,

Brian