code: def _create_index_files(root_dir, force_no_processing=False):
      
      # Initialise list of created file paths to build up as we make them
      created_files = []
      # Walk the root dir downwards, creating index files as we go
      for here, dirs, files in os.walk(root_dir):
          print('Processing %s' % here)
          # Sort the subdirectories by name
          dirs = sorted(dirs)
          # Get image files - all files in the directory matching IMAGE_FILE_REGEX
          image_files = [f for f in files if re.match(IMAGE_FILE_REGEX, f)]
          # Sort the image files by name
          image_files = sorted(image_files)
          # Create this directory's index file and add its name to the created
          # files list
          created_files.append(
              _create_index_file(
                  root_dir, here, image_files, dirs, force_no_processing
              )
          )
      # Return the list of created files
      return created_files
docs: Crawl the root directory downwards, generating an index HTML file in each
      directory on the way down.
      @param {String} root_dir - The top level directory to crawl down from. In
          normal usage, this will be '.'.
      @param {Boolean=False} force_no_processing - If True, do not attempt to
          actually process thumbnails, PIL images or anything. Simply index
          <img> tags with original file src attributes.
      @return {[String]} Full file paths of all created files.