Query that plucks tags from Structure field

I have a tag field inside a structure field. I’d like to autocomplete this field by querying all of the other pages. I’ve done this successfully many times with tags, but never from inside a structure field.

    type: structure
            type: tags
            options: query
            query: page.parent.childrenAndDrafts.pluck("kiez", ",", true)
            max: 1

This does not work. How do I get the query to look inside the structure field?

I think you need a custom method to achieve this, pluck only works with single value fields or fields with comma etc. separated values.