class_docstr: A Starcraft II environment.
  
  The implementation details of the action and observation specs are in
  lib/features.py
code: def _step_to(self, game_loop, current_game_loop):
      step_mul = game_loop - current_game_loop
      if step_mul < 0:
          raise ValueError("We should never need to step backwards")
      if step_mul > 0:
          with self._metrics.measure_step_time(step_mul):
              if not self._controllers[
                  0
              ].status_ended:  # May already have ended.
                  self._parallel.run(
                      (c.step, step_mul) for c in self._controllers
                  )
  
imports: import collections
  import copy
  import random
  import time
  from absl import logging
  from pysc2 import maps
  from pysc2 import run_configs
  from pysc2.env import enums
  from pysc2.env import environment
  from pysc2.lib import actions
  from pysc2.lib import features
  from pysc2.lib import metrics
  from pysc2.lib import portspicker
  from pysc2.lib import renderer_human
  from pysc2.lib import run_parallel
  from pysc2.lib import stopwatch
  from s2clientprotocol import sc2api_pb2
label_desc: Use image node_id 18 for calling the SC2Env obj's underlying member method code with example usage: obj._step_to(game_loop, current_game_loop) without return types