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. \nThe available levels are: \n{}".format(
                  ", ".join(sorted(self.levels.keys()))
              ),
              crash=True,
          )
      selected_level = (
          self.selected_level.lower()
          if self.force_lower
          else self.selected_level
      )
      if selected_level not in self.levels.keys():
          logger.screen.error(
              "The selected level ({}) is not part of the available levels ({})".format(
                  selected_level, ", ".join(self.levels.keys())
              ),
              crash=True,
          )
      return self.levels[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 2 for calling the SingleLevelSelection obj's underlying member method code with example usage: obj.__str__() and returns: self