So the filter would look something like...?

```ruby
table.filter(parent_ids: [1,2,3]) do |item, data|
  !data[:parent_ids].include?(item[foreign_key])
end
```

I'm not sure I've fully grokked, but it doesn't seem unreasonable to reuse that so long as it doesn't significantly complicate the implementation. Otherwise, this seems specialized enough that maybe we should wait for another use case.