def get_function_url(self, function):
        """
        Registers the given callable in the system (if it isn't already)
        and returns the URL that can be used to invoke the given function from remote.
        """
        assert self._opened, "RPC System is not opened"
        logging.debug("get_function_url(%s)" % repr(function))
        if function in ~self._functions:
            functionid = self._functions[:function]
        else:
            functionid = uuid.uuid1()
            self._functions[functionid] = function
        return "anycall://%s/functions/%s" % (self._connectionpool.ownid, functionid.hex)
Registers the given callable in the system (if it isn't already)
        and returns the URL that can be used to invoke the given function from remote.