code: def set_file_mode(path, spec, fd=None):
      
      if isinstance(spec, int):
          new_mode = spec
      elif not mitogen.core.PY3 and isinstance(spec, long):
          new_mode = spec
      elif spec.isdigit():
          new_mode = int(spec, 8)
      else:
          mode = os.stat(path).st_mode
          new_mode = apply_mode_spec(spec, mode)
  
      if fd is not None and hasattr(os, 'fchmod'):
          os.fchmod(fd, new_mode)
      else:
          os.chmod(path, new_mode)
docs: Update the permissions of a file using the same syntax as chmod(1).