docstr: Assert that maximum number of placement groups is enforced.
docstr_tok: ["Assert","that","maximum","number","of","placement","groups","is","enforced","."]
code: def testPlacementGroupLimitedRequests(self):
      """Assert that maximum number of placement groups is enforced."""
      os.environ["TUNE_MAX_PENDING_TRIALS_PG"] = "6"
      self.testPlacementGroupRequests(scheduled=6)
  
imports: import sys
  import os
  import time
  import numpy
  import unittest
  import ray
  from ray import tune
  from ray.tune.execution.ray_trial_executor import RayTrialExecutor
  from ray.tune.experiment import Trial
  from ray.tune import Callback
  from ray.tune.execution.trial_runner import TrialRunner
  from ray.tune.execution.placement_groups import PlacementGroupFactory
  from ray.util import placement_group_table
  from ray.cluster_utils import Cluster
  from ray.rllib import _register_all
label_desc: Use image node_id 6 for calling the TrialRunnerPlacementGroupTest obj's underlying member method code with example usage: obj.testPlacementGroupLimitedRequests() without return types