code: def open_and_prefetch_cache(self, file_name, file_names_to_prefetch):
      cp_file_names = [cf.file_name for cf in self._cache_prefetchers]
      # print('cp files', cp_file_names)
      result = None
      for cf in self._cache_prefetchers:
          if cf.check_if_hit(file_name):
              result = cf.read()
              break
      if not result:
          # print("no hit", file_name)
          result = cf.read_cache(file_name, self._variables)
      cp_file_names = [cf.file_name for cf in self._cache_prefetchers]
      for i, fn in enumerate(cp_file_names):
          if fn and fn not in file_names_to_prefetch:
              self._cache_prefetchers[
                  i
              ].read()  # waste prefetched cache
              # print("wasted", fn)
      for fn in file_names_to_prefetch:
          if fn not in cp_file_names:
              try:
                  index = cp_file_names.index(None)
                  cp_file_names[index] = fn
                  self._cache_prefetchers[index].request(
                      cp_file_names[index]
                  )
              except:
                  continue
      return result
  
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 2 for calling the CacheReaderWithPrefetch obj's underlying member method code with example usage: obj.open_and_prefetch_cache(file_name, file_names_to_prefetch) and returns: result