Original fictional self-practice. No account, website database, cloud resource or paid API. Unzip into a new local directory; copy extension_reference.py.txt to extension_reference.py and run python3 extension_reference.py --source . with Python 3.9+. Read each CSV’s header and the lesson’s exact grain/units first. The code is a transparent control for the supplied small fixtures, not a general production ingestion library. Make changed-input tests in a separate copy and retain source evidence.