code: def __str__(self):
      if self.selected_level is None:
          logger.screen.error(
              "No level has been selected. Please select a level using the -lvl command line flag, "
              "or change the level in the preset.",
              crash=True,
          )
      return self.selected_level
  
imports: import operator
  import time
  from collections import OrderedDict
  from typing import Union, List, Tuple, Dict
  import numpy
  from rl_coach import logger
  from rl_coach.base_parameters import Parameters
  from rl_coach.base_parameters import VisualizationParameters
  from rl_coach.core_types import GoalType, ActionType, EnvResponse, RunPhase
  from rl_coach.environments.environment_interface import EnvironmentInterface
  from rl_coach.logger import screen
  from rl_coach.renderer import Renderer
  from rl_coach.spaces import ActionSpace, ObservationSpace, DiscreteActionSpace, RewardSpace, StateSpace
  from rl_coach.utils import squeeze_list, force_list
label_desc: Use image node_id 3 for calling the LevelSelection obj's underlying member method code with example usage: obj.__str__() and returns: self