code: def addprefix(subject, prefix):
    
  
    if not prefix:
      return subject
    dir_, base = split(subject)
    if callable(prefix):
      base = prefix(base)
    else:
      base = prefix + base
    return join(dir_, base)
docs: Adds the specified *prefix* to the last path element in *subject*.
    If *prefix* is a callable, it must accept exactly one argument, which
    is the last path element, and return a modified value.