code: def on_environment_created(
      self, *, worker, sub_environment, env_context, **kwargs
  ):
      # Create a vector-index-sum property per remote worker.
      if not hasattr(worker, "sum_sub_env_vector_indices"):
          worker.sum_sub_env_vector_indices = 0
      # Add the sub-env's vector index to the counter.
      worker.sum_sub_env_vector_indices += env_context.vector_index
      print(
          f"sub-env {sub_environment} created; "
          f"worker={worker.worker_index}; "
          f"vector-idx={env_context.vector_index}"
      )
  
imports: from collections import Counter
  import unittest
  import ray
  from ray.rllib.algorithms.callbacks import DefaultCallbacks
  from ray.rllib.algorithms.ppo import PPOConfig
  from ray.rllib.env.single_agent_env_runner import SingleAgentEnvRunner
  from ray.rllib.utils.test_utils import framework_iterator
label_desc: Use image node_id 1 for calling the OnEnvironmentCreatedCallback obj's underlying member method code with example usage: obj.on_environment_created() without return types