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Test cases and examples, explaining some edge cases (avoidable if keep ids as strings)

Prevent the python sqlite named placeholders, aka 'named style' (https://docs.python.org/3/library/sqlite3.html) in the traversal CTEs from leaking into the go constants, which expects all qmark style

Corresponding updates to tests: the type of the seed wil now match the output; all the remaining results are still strings