The code in https://github.com/firebase/extensions/blob/master/firestore-bigquery-export/scripts/import/src/index.ts#L84 makes reference to config.transformFunctionUrl

However, this property is never actually ever provided by the config here:
https://github.com/firebase/extensions/blob/master/firestore-bigquery-export/scripts/import/src/config.ts

The config.ts file needs to be updated to return

{
...restOfConfig,
transformFunctionUrl: program.transformFunctionUrl,
}