class_docstr: Get data from file cache directly.
code: def close(self):
      if (
          hasattr(self, "_cache_reader_with_prefetch")
          and self._cache_reader_with_prefetch
      ):
          self._cache_reader_with_prefetch.close()
          self._cache_reader_with_prefetch = None
  
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 7 for calling the CacheDataSource obj's underlying member method code with example usage: obj.close() without return types