code: def _locate_files_to_delete(algorithm, rotated_files, next_rotation_id):
      
      rotation_slot = algorithm.id_to_slot(next_rotation_id)
      for a_path, a_rotation_id in rotated_files:
          if rotation_slot == algorithm.id_to_slot(a_rotation_id):
              yield a_path
docs: Looks for hanoi_rotator generated files that occupy the same slot
      that will be given to rotation_id.