Python review pass

Failures

• Any bare except or except Exception that continues?
• Any exception caught and dropped without a reason?
• Is the cause chained on every re-raise?
• Can a caller tell "no result" from "lookup failed"?

Traps

• Any mutable default argument?
• Any collection mutated while iterated?
• Is every opened resource closed by a with?
• Any truthiness check where zero or empty is a valid value?

Types

• Do the hints admit None everywhere it can occur?
• Any dict with a fixed known shape that should be a dataclass?

Dependencies

• Anything added that the standard library already does?
• Anything added for a single function?

Tests

• Does a new test fail if the change is reverted?
• Is the raising path covered, not only the happy path?