Nested object options and TypeScript aren't compatible

Using object options

If I want to pass object options, like tool --bq.project=zzz
then how should I describe the option?

I tried as

        .option(
            'bq.project',
            {type: 'string', description: 'GCP project id for BigQuery'})

but in TypeScript it doesn't work.
I do see intellisence for argv['bq.project'] but it's not correct (it returns undefined), the correct call is argv.bg.project, but in TypeScript is not legal, because argv has no 'bq' field.
Of cause with the casting (<any>argv.bq).project it works, but it's ugly.

Start with docs/tricks.md's object-options guidance and reproduce the bq.project example from the issue. Inspect how the option declaration and argv access are typed; done means nested object options have accurate TypeScript access without an any cast.