code: def check_if_hit(self, fn):
      self._lock.acquire()
      if fn == self.file_name:
          self.file_name = None
          self._lock.release()
          return True
      self._lock.release()
      return False
  
imports: import atexit
  import csv
  import os
  import threading
  from collections import OrderedDict, deque
  from time import sleep
  import numpy
  from nnabla.config import nnabla_config
  from nnabla.logger import logger
  from nnabla.utils.communicator_util import current_communicator
  from six.moves import queue
  from .data_source import DataSource
  from .data_source_loader import FileReader, load
label_desc: Use image node_id 5 for calling the CachePrefetcher obj's underlying member method code with example usage: obj.check_if_hit(fn) and returns: False, True