code: def index_directory(
      directory,
      labels,
      formats,
      class_names=None,
      shuffle=True,
      seed=None,
      follow_links=False,
  ):
      """Make list of all files in the subdirs of `directory`, with their labels.
  
      # Arguments
        directory: The target directory (string).
        labels: Either "inferred"
            (labels are generated from the directory structure),
            None (no labels),
            or a list/tuple of integer labels of the same size as the number of
            valid files found in the directory. Labels should be sorted according
            to the alphanumeric order of the image file paths
            (obtained via `os.walk(directory)` in Python).
        formats: Allowlist of file extensions to index (e.g. ".jpg", ".txt").
        class_names: Only valid if "labels" is "inferred". This is the explicit
            list of class names (must match names of subdirectories). Used
            to control the order of the classes
            (otherwise alphanumerical order is used).
        shuffle: Whether to shuffle the data. Default: True.
            If set to False, sorts the data in alphanumeric order.
        seed: Optional random seed for shuffling.
        follow_links: Whether to visits subdirectories pointed to by symlinks.
  
      # Returns
        tuple (file_paths, labels, class_names).
          file_paths: list of file paths (strings).
          labels: list of matching integer labels (same length as file_paths)
          class_names: names of the classes corresponding to these labels, in
              order.
      """
      subdirs = []
      for subdir in sorted(os.listdir(directory)):
          if os.path.isdir(os.path.join(directory, subdir)):
              subdirs.append(subdir)
      if not class_names:
          class_names = subdirs
      else:
          if set(class_names) != set(subdirs):  # pragma: no cover
              raise ValueError(  # pragma: no cover
                  "The `class_names` passed did not match the "
                  "names of the subdirectories of the target directory. "
                  "Expected: %s, but received: %s"
                  % (subdirs, class_names)
              )
      class_indices = dict(zip(class_names, range(len(class_names))))
  
      # Build an index of the files
      # in the different class subfolders.
      pool = multiprocessing.pool.ThreadPool()
      results = []
      filenames = []
  
      for dirpath in (
          os.path.join(directory, subdir) for subdir in subdirs
      ):
          results.append(
              pool.apply_async(
                  index_subdirectory,
                  (dirpath, class_indices, follow_links, formats),
              )
          )
      labels_list = []
      for res in results:
          partial_filenames, partial_labels = res.get()
          labels_list.append(partial_labels)
          filenames += partial_filenames
      i = 0
      labels = np.zeros((len(filenames),), dtype="int32")
      for partial_labels in labels_list:
          labels[i : i + len(partial_labels)] = partial_labels
          i += len(partial_labels)
  
      print(
          "Found %d files belonging to %d classes."
          % (len(filenames), len(class_names))
      )
      pool.close()
      pool.join()
      file_paths = [
          os.path.join(directory, fname) for fname in filenames
      ]
  
      if shuffle:
          # Shuffle globally to erase macro-structure
          if seed is None:
              seed = np.random.randint(1e6)  # pragma: no cover
          rng = np.random.RandomState(seed)
          rng.shuffle(file_paths)
          rng = np.random.RandomState(seed)
          rng.shuffle(labels)
      return file_paths, labels, class_names
  
file_path: autokeras/autokeras/utils/io_utils.py
imports: import json
  import multiprocessing
  import os
  from typing import Optional
  from typing import Tuple
  import numpy
  import tensorflow
  from keras_tuner.engine import hyperparameters
label_desc: Use image node_id 3 for calling a global function with example usage: index_directory(directory, labels, formats, class_names, shuffle, seed, follow_links) and returns: file_paths,  labels,  class_names