class_docstr: Integration test for PreemptionCheckpointHandler.
class_docstr_tok: ["Integration","test","for","PreemptionCheckpointHandler","."]
code: def _maybe_trigger_a_preemption(
      self, training_started_event, trigger_it=False
  ):
      if not training_started_event:
          return
      clear_events = [
          event
          for event in training_started_event
          if not event.is_set()
      ]
      if clear_events:
          if trigger_it:
              logging.info("Set preemption signal")
              clear_events[0].set()
          elif random.randrange(0, 9) > 6:
              clear_events[0].set()
  
imports: import os
  import random
  import re
  import signal
  import sys
  import threading
  import time
  from absl.testing import parameterized
  from tensorflow.python.checkpoint import checkpoint
  from tensorflow.python.checkpoint import checkpoint_management
  from tensorflow.python.distribute import collective_all_reduce_strategy
  from tensorflow.python.distribute import combinations
  from tensorflow.python.distribute import distribute_lib
  from tensorflow.python.distribute import mirrored_strategy
  from tensorflow.python.distribute import multi_process_runner
  from tensorflow.python.distribute import multi_worker_test_base
  from tensorflow.python.distribute import multi_worker_util
  from tensorflow.python.distribute import one_device_strategy
  from tensorflow.python.distribute import test_util
  from tensorflow.python.distribute.failure_handling import failure_handling
  from tensorflow.python.distribute.failure_handling import failure_handling_util
  from tensorflow.python.eager import def_function
  from tensorflow.python.framework import config
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import errors_impl
  from tensorflow.python.module import module
  from tensorflow.python.ops import variables
  from tensorflow.python.platform import gfile
  from tensorflow.python.platform import test
  from tensorflow.python.platform import tf_logging
  from tensorflow.python.training import server_lib
label_desc: Use image node_id 1 for calling the PreemptionCheckpointTest obj's underlying member method code with example usage: obj._maybe_trigger_a_preemption(training_started_event, trigger_it) without return types