code: def get_filenames(dir, cifar_classnum):
      assert cifar_classnum == 10 or cifar_classnum == 100
      if cifar_classnum == 10:
          train_files = [
              os.path.join(
                  dir, "cifar-10-batches-py", "data_batch_%d" % i
              )
              for i in range(1, 6)
          ]
          test_files = [
              os.path.join(dir, "cifar-10-batches-py", "test_batch")
          ]
          meta_file = os.path.join(
              dir, "cifar-10-batches-py", "batches.meta"
          )
      elif cifar_classnum == 100:
          train_files = [os.path.join(dir, "cifar-100-python", "train")]
          test_files = [os.path.join(dir, "cifar-100-python", "test")]
          meta_file = os.path.join(dir, "cifar-100-python", "meta")
      return train_files, test_files, meta_file
  
imports: import numpy
  import os
  import pickle
  import tarfile
  from ...utils import logger
  from ...utils.fs import download, get_dataset_path
  from ..base import RNGDataFlow
label_desc: Use image node_id 3 for calling a global function with example usage: get_filenames(dir, cifar_classnum) and returns: train_files,  test_files,  meta_file