def suggest_path(root_dir):
if not root_dir:<EOL><INDENT>return [os.path.abspath(os.sep), '<STR_LIT>', os.curdir, os.pardir]<EOL><DEDENT>if '<STR_LIT>' in root_dir:<EOL><INDENT>root_dir = os.path.expanduser(root_dir)<EOL><DEDENT>if not os.path.exists(root_dir):<EOL><INDENT>root_dir, _ = os.path.split(root_dir)<EOL><DEDENT>return list_path(root_dir)<EOL>
List all files and subdirectories in a directory.
    If the directory is not specified, suggest root directory,
    user directory, current and parent directory.
    :param root_dir: string: directory to list
    :return: list