This uses gtfs-via-duckdb.
curl -fsSL \
'https://mobility-api.mobility-database.fintraffic.fi/gtfs-realtime/v2/' \
-H 'accept: application/protobuf' \
-H "x-api-key: $api_key" \
| ~/web/print-gtfs-rt-cli/cli.js -j \
| duckdb -readonly -csv -f match.sql gtfs/fintraffic.gtfs.duckdb \
| qsv select '!item' | head -n 10