code: import sys
  import threading
  import queue
  import random
  import collections
  
  import torch
  import torch.multiprocessing as multiprocessing
  
  # from torch._C import _set_worker_signal_handlers, _update_worker_pids, \
  #     _remove_worker_pids, _error_if_any_worker_fails
  # from torch.utils.data.dataloader import DataLoader
  # from torch.utils.data.dataloader import _DataLoaderIter
  # from torch.utils.data.dataloader import ManagerWatchdog
  # from torch.utils.data.dataloader import _pin_memory_loop
  # from torch.utils.data.dataloader import MP_STATUS_CHECK_INTERVAL
  
  # from torch.utils.data.dataloader import ExceptionWrapper
  # from torch.utils.data.dataloader import _use_shared_memory
  # from torch.utils.data.dataloader import numpy_type_map
  # from torch.utils.data.dataloader import default_collate
  # from torch.utils.data.dataloader import pin_memory_batch
  # from torch.utils.data.dataloader import _SIGCHLD_handler_set
  # from torch.utils.data.dataloader import _set_SIGCHLD_handler
  
  ###for pytorch 1.1
  from torch._C import _set_worker_signal_handlers
  from torch.utils.data import _utils
  from torch.utils.data.dataloader import DataLoader
  from torch.utils.data.dataloader import _DataLoaderIter
   
  _use_shared_memory = False
  
  
  if sys.version_info[0] == 2:
      import Queue as queue
  else:
      import queue
  
  def _ms_loop(dataset, index_queue, data_queue, done_event, collate_fn, scale, seed, init_fn, worker_id):
      try:
          global _use_shared_memory
          _use_shared_memory = True
          _set_worker_signal_handlers()
  
          torch.set_num_threads(1)
          random.seed(seed)
          torch.manual_seed(seed)
          data_queue.cancel_join_thread()
  
          if init_fn is not None:
              init_fn(worker_id)
  
  #         watchdog = ManagerWatchdog()
          watchdog = _utils.worker.ManagerWatchdog()
  
          while watchdog.is_alive():
  #             try:
  #                 r = index_queue.get(timeout=MP_STATUS_CHECK_INTERVAL)
              try:
                  r = index_queue.get(timeout=_utils.MP_STATUS_CHECK_INTERVAL)
              except queue.Empty:
                  continue
  
              if r is None:
                  assert done_event.is_set()
                  return
              elif done_event.is_set():
                  continue
              idx, batch_indices = r
              try:
                  idx_scale = 0
                  if len(scale) > 1 and dataset.train:
                      idx_scale = random.randrange(0, len(scale))
                      dataset.set_scale(idx_scale)
  
                  samples = collate_fn([dataset[i] for i in batch_indices])
                  samples.append(idx_scale)
  #             except Exception:
  #                 data_queue.put((idx, ExceptionWrapper(sys.exc_info())))
              except Exception:
                  data_queue.put((idx, _utils.ExceptionWrapper(sys.exc_info())))
              else:
                  data_queue.put((idx, samples))
      except KeyboardInterrupt:
          pass
  
  class _MSDataLoaderIter(_DataLoaderIter):
      def __init__(self, loader):
          self.dataset = loader.dataset
          self.scale = loader.scale
          self.collate_fn = loader.collate_fn
          self.batch_sampler = loader.batch_sampler
          self.num_workers = loader.num_workers
          self.pin_memory = loader.pin_memory and torch.cuda.is_available()
          self.timeout = loader.timeout
  
          self.sample_iter = iter(self.batch_sampler)
  
          base_seed = torch.LongTensor(1).random_().item()
  
          if self.num_workers > 0:
              self.worker_init_fn = loader.worker_init_fn
              self.worker_queue_idx = 0
              self.worker_result_queue = multiprocessing.Queue()
              self.batches_outstanding = 0
              self.worker_pids_set = False
              self.shutdown = False
              self.send_idx = 0
              self.rcvd_idx = 0
              self.reorder_dict = {}
              self.done_event = multiprocessing.Event()
  
              base_seed = torch.LongTensor(1).random_()[0]
  
              self.index_queues = []
              self.workers = []
              for i in range(self.num_workers):
                  index_queue = multiprocessing.Queue()
                  index_queue.cancel_join_thread()
                  w = multiprocessing.Process(
                      target=_ms_loop,
                      args=(
                          self.dataset,
                          index_queue,
                          self.worker_result_queue,
                          self.done_event,
                          self.collate_fn,
                          self.scale,
                          base_seed + i,
                          self.worker_init_fn,
                          i
                      )
                  )
                  w.start()
                  self.index_queues.append(index_queue)
                  self.workers.append(w)
  
              if self.pin_memory:
                  self.data_queue = queue.Queue()
                  pin_memory_thread = threading.Thread(
  #                     target=_pin_memory_loop,
                      target=_utils.pin_memory._pin_memory_loop,
                      args=(
                          self.worker_result_queue,
                          self.data_queue,
                          torch.cuda.current_device(),
                          self.done_event
                      )
                  )
                  pin_memory_thread.daemon = True
                  pin_memory_thread.start()
                  self.pin_memory_thread = pin_memory_thread
              else:
                  self.data_queue = self.worker_result_queue
  
  #             _update_worker_pids(id(self), tuple(w.pid for w in self.workers))
  #             _set_SIGCHLD_handler()
              _utils.signal_handling._set_worker_pids(id(self), tuple(w.pid for w in self.workers))
              _utils.signal_handling._set_SIGCHLD_handler()
              self.worker_pids_set = True
  
              for _ in range(2 * self.num_workers):
                  self._put_indices()
  
  class MSDataLoader(DataLoader):
      def __init__(
          self, args, dataset, batch_size=1, shuffle=False,
          sampler=None, batch_sampler=None,
          collate_fn=_utils.collate.default_collate, pin_memory=False, drop_last=False,
          timeout=0, worker_init_fn=None):
  
          super(MSDataLoader, self).__init__(
              dataset,
              batch_size=batch_size,
              shuffle=shuffle,
              sampler=sampler,
              batch_sampler=batch_sampler,
              num_workers=args.n_threads,
              collate_fn=collate_fn,
              pin_memory=pin_memory,
              drop_last=drop_last,
              timeout=timeout,
              worker_init_fn=worker_init_fn
          )
  
          self.scale = args.scale
  
      def __iter__(self):
          return _MSDataLoaderIter(self)
  
apis: torch.utils.data._utils.worker.ManagerWatchdog torch.multiprocessing.Event torch.manual_seed torch.multiprocessing.Queue torch.cuda.current_device torch._C._set_worker_signal_handlers torch.set_num_threads torch.cuda.is_available torch.utils.data._utils.signal_handling._set_SIGCHLD_handler torch.LongTensor torch.multiprocessing.Process