code: def get_files(input_file):
    
    file_index = {}
    base_dir = None
    if os.path.isfile(input_file):
      file_index[input_file] = None
      base_dir = os.path.dirname(input_file)
    elif os.path.isdir(input_file):
      base_dir = input_file
      for inf in glob.glob(input_file + s.SBP_EXTENSION):
        file_index[os.path.abspath(inf)] = None
      for inf in glob.glob(input_file + '/*'):
        base, index = get_files(os.path.abspath(inf))
        z = file_index.copy()
        z.update(index)
        file_index = z
    return (base_dir, file_index)
docs: Initializes an index of files to generate, returns the base
    directory and index.