code: def check_obs(obs, env):
      assert len(obs) == 2, "two players"
      for key, player_obs in obs.items():
          assert isinstance(
              player_obs, int
          )  # .shape == (env.NUM_STATES)
          assert player_obs < env.NUM_STATES
  
file_path: ray/python/ray/rllib/examples/env/tests/test_matrix_sequential_social_dilemma.py
imports: import random
  from ray.rllib.examples.env.matrix_sequential_social_dilemma import IteratedPrisonersDilemma, IteratedChicken, IteratedStagHunt, IteratedBoS
label_desc: Use image node_id 3 for calling a global function with example usage: check_obs(obs, env) without return types