def METHOD_NAME(start_path):
    """Print a tree of files in a directory."""
    for root, _, files in os.walk(start_path):
        level = root.replace(start_path, "").count(os.sep)
        indent = " " * 4 * level
        print(f"{indent}{os.path.basename(root)}/")
        sub_indent = " " * 4 * (level + 1)
        for file in sorted(files):
            print(sub_indent + file)