text: _bt_1 = ['s(',
               'DO_PickGearPart[]',
               'DO_MoveGearPart[P: place]',
               'DO_PlaceGearPart[]',
           ')']
  
  _bt_2 = ['f(',
               'CHECK_GearPartPlaced[]',
               's(',
                   'DO_PickGearPart[]',
                   'DO_MoveGearPart[P: place]',
                   'DO_PlaceGearPart[]',
               ')',
           ')']
  
  
  def select_bt(idx: int):
      collection = [_bt_1, _bt_2]
      return collection[idx]
  