code: def _test_episode_length(self, env, length):
      self.assert_reset(env)
      for _ in range(length - 1):
          self.assert_mid_step(env)
      self.assert_last_step(env)
  
      self.assert_first_step(env)
      for _ in range(length - 1):
          self.assert_mid_step(env)
      self.assert_last_step(env)
  
imports: from absl.testing import absltest
  import mock
  import numpy
  from pysc2.env import enums
  from pysc2.env import environment
  from pysc2.env import mock_sc2_env
  from pysc2.env import sc2_env
  from pysc2.lib import features
  from s2clientprotocol import common_pb2
  from s2clientprotocol import raw_pb2
  from s2clientprotocol import sc2api_pb2
label_desc: Use image node_id 8 for calling the _TestMixin obj's underlying member method code with example usage: obj._test_episode_length(env, length) without return types