code: def print_state(self):
          
  
          def tile_string(value):
              """Concert value to string."""
              if value > 0:
                  return '% 5d' % (2 ** value,)
              return "     "
  
          separator_line = '-' * 25
          print(separator_line)
          for row in range(4):
              print("|" + "|".join([tile_string(v) for v in self._state[row, :]]) + "|")
              print(separator_line)
docs: Prints the current state.