code: def trace_symlink_target(link):
  	
  
  	if not is_symlink(link):
  		raise ValueError("link must point to a symlink on the system")
  	while is_symlink(link):
  		orig = os.path.dirname(link)
  		link = readlink(link)
  		link = resolve_path(link, orig)
  	return link
docs: Given a file that is known to be a symlink, trace it to its ultimate
  	target.
  
  	Raises TargetNotPresent when the target cannot be determined.
  	Raises ValueError when the specified link is not a symlink.