code: def wrap(cls, url):
      
      if isinstance(url, cls):
        return url
      elif isinstance(url, compatible_string):
        return cls(url)
      else:
        raise ValueError('url must be either a string or Link.')
docs: Given a url that is either a string or :class:`Link`, return a :class:`Link`.
  
      :param url: A string-like or :class:`Link` object to wrap.
      :returns: A :class:`Link` object wrapping the url.