After one pass, you should be able to answer three questions:
Where does the default .env path come from?
When does a parsed key change os.environ?
What changes when the file is missing or override=True is used?
Each answer is one hover away. The five nodes name the functions that own the work. The ten edges point at the call, the return, and the two branches of the override rule.
The graph keeps the answer narrow. It does not explain every supported .env syntax, CLI command, or framework integration.