def watch_token(method):
method._kxg_watch_token = True<EOL>return method<EOL>
Mark a token extension method that should automatically be called when a 
token method of the same name is called.

This decorator must only be used on TokenExtension methods, otherwise it 
will silently do nothing.  The reason is that the decorator itself can't do 
anything but label the given method, because at the time of decoration the 
token to watch isn't known.  The method is actually setup to watch a token 
in the TokenExtension constructor, which searches for the label added here.  
But other classes won't make this search and will silently do nothing.