code: def _pb2_importer():
      # PB2 introduces a GPy dependency which can be expensive, so we import
      # lazily.
      from ray.tune.schedulers.pb2 import PB2
  
      return PB2
  
file_path: ray/python/ray/tune/schedulers/__init__.py
imports: import inspect
  from ray._private.utils import get_function_args
  from ray.tune.schedulers.trial_scheduler import TrialScheduler, FIFOScheduler
  from ray.tune.schedulers.hyperband import HyperBandScheduler
  from ray.tune.schedulers.hb_bohb import HyperBandForBOHB
  from ray.tune.schedulers.async_hyperband import AsyncHyperBandScheduler, ASHAScheduler
  from ray.tune.schedulers.median_stopping_rule import MedianStoppingRule
  from ray.tune.schedulers.pbt import PopulationBasedTraining, PopulationBasedTrainingReplay
  from ray.tune.schedulers.resource_changing_scheduler import ResourceChangingScheduler
  from ray.util import PublicAPI
label_desc: Use image node_id 1 for calling a global function with example usage: _pb2_importer() and returns: PB2