code: def test_main_process_first(self):
      tmpdirname = ""
      try:
          my_rank = DistributedHelper.rank
          if DistributedHelper.is_main_process:
              tmpdirname = tempfile.mkdtemp()
  
          tmpdirname = DistributedHelper.broadcast_object(tmpdirname)
  
          with DistributedHelper.main_process_first():
              for _ in range(2):
                  time.sleep(0.1 + my_rank * 0.05)
                  files = list(os.listdir(tmpdirname))
                  if DistributedHelper.is_main_process:
                      self.assertEqual(0, len(files))
                  else:
                      self.assertIn(f"rank0", files)
                      self.assertNotIn(f"rank{my_rank}", files)
  
              with open(
                  os.path.join(tmpdirname, f"rank{my_rank}"), "w"
              ) as f:
                  f.write("ok")
  
              for _ in range(2):
                  time.sleep(0.1 + my_rank * 0.05)
                  files = list(os.listdir(tmpdirname))
                  if DistributedHelper.is_main_process:
                      self.assertEqual(1, len(files))
                      self.assertIn(f"rank0", files)
                  else:
                      self.assertIn(f"rank0", files)
                      self.assertIn(f"rank{my_rank}", files)
  
          DistributedHelper.barrier()
          files = set(os.listdir(tmpdirname))
          expect = set(
              [
                  f"rank{rnk}"
                  for rnk in range(DistributedHelper.world_size)
              ]
          )
          self.assertSetEqual(expect, files)
          DistributedHelper.barrier()
      finally:
          if (
              tmpdirname is not None
              and DistributedHelper.is_main_process
          ):
              shutil.rmtree(tmpdirname)
  
imports: import os
  import random
  import shutil
  import tempfile
  import time
  import unittest
  import numpy
  import torch
  import torch.distributed
  from torch.nn import Module
  from torch.nn.parallel import DistributedDataParallel
  from avalanche.benchmarks.scenarios.deprecated.generators import dataset_benchmark
  from avalanche.benchmarks.utils.classification_dataset import _make_taskaware_tensor_classification_dataset
  from avalanche.distributed import DistributedHelper
  from avalanche.distributed.distributed_helper import RollingSeedContext, BroadcastSeedContext
  from avalanche.models import SimpleMLP, as_multitask
  from avalanche.models.utils import avalanche_model_adaptation
  from avalanche.training.determinism.rng_manager import RNGManager
  from tests.distributed.distributed_test_utils import check_skip_distributed_slow_test, check_skip_distributed_test, suppress_dst_tests_output, common_dst_tests_setup
label_desc: Use image node_id 18 for calling the DistributedHelperTests obj's underlying member method code with example usage: obj.test_main_process_first() without return types