code: def chmod_native(path, mode_expression, recursive=False):
    
    popenargs = ["chmod"]
    if recursive:
      popenargs.append("-R")
    popenargs.append(mode_expression)
    popenargs.append(path)
    subprocess.check_call(popenargs)
docs: This is ugly and will only work on POSIX, but the built-in Python os.chmod support
    is very minimal, and neither supports fast recursive chmod nor "+X" type expressions,
    both of which are slow for large trees. So just shell out.