code: def issub(path):
    
  
    if isabs(path):
      return False
    if path.startswith(curdir + sep) or path.startswith(pardir + sep) or \
        path == curdir or path == pardir:
      return False
    return True
docs: Returns #True if *path* is a relative path that does not point outside
    of its parent directory or is equal to its parent directory (thus, this
    function will also return False for a path like `./`).