private function getFightersByEntity($fighters): Collection
    {
        // Right now, we are treating users and teams as equals.
        // It doesn't matter right now, because we only need name attribute which is common to both models

        // $this->groupBy contains federation_id, association_id, club_id, etc.
        if (($this->groupBy) != null) {
            return $fighters->groupBy($this->groupBy); // Collection of Collection
        }

        return $fighters->chunk(1); // Collection of Collection
    }