def callable(self, *args, **kwargs):
        """Decorate a request handler with a handler tool callable."""
        innerfunc = cherrypy.serving.request.handler

        def wrap(*args, **kwargs):
            return self.newhandler(innerfunc, *args, **kwargs)

        cherrypy.serving.request.handler = wrap
Decorate a request handler with a handler tool callable.
cherrypy/_cptools.py