code: func (a Audiences) Intersect(tauds Audiences) Audiences {
  	selected := Audiences{}
  	for _, taud := range tauds {
  		if a.Has(taud) {
  			selected = append(selected, taud)
  		}
  	}
  	return selected
  }
docs: // Intersect intersects Audiences with a target Audiences and returns all
  // elements in both.