Dgraph, @groupby after @cascade

Question

As of the date of the post, the Dgraph doesn't have the nested filtering feature. The only way to do it is to use the @cascade directive. I have to create a query variable to do the next step, which is @groupby, in my case. However, @cascade is a post-processing step, so @groupby completely misses filtered options.

Is there a way to construct the query to do the job?

Example: show how many companies in each sector have registered in a certain country.

type Company {
  uid
  sector: [string]
  address: [uid]
}
type Address {
  uid
  country: [string]
}
-------------------------------------------
  var(func: type(Company)) @cascade {
    c as uid
    sector
    address @filter(eq(country, "$country")) {
      uid
    }
  }
  countries(func: uid(c)) @groupby(sector) {
      count(uid)
  }