protected function definingClassForAction($actionOrigCasing)
    {
        $action = strtolower($actionOrigCasing);

        $definingClass = null;
        $insts = array_merge([$this], (array) $this->getExtensionInstances());
        foreach ($insts as $inst) {
            if (!method_exists($inst, $action)) {
                continue;
            }
            $r = new ReflectionClass(get_class($inst));
            $m = $r->getMethod($actionOrigCasing);
            return $m->getDeclaringClass()->getName();
        }
        return null;
    }