private function readMethodCallees($class, ReflectionMethod $method)
    {
        $callees = array();

        // read parent annotations
        try {
            $prototype = $method->getPrototype();
            // error occurs on every second PHP stable release - getPrototype() returns itself
            if ($prototype->getDeclaringClass()->getName() !== $method->getDeclaringClass()->getName()) {
                $callees = array_merge($callees, $this->readMethodCallees($class, $prototype));
            }
        } catch (ReflectionException $e) {
        }

        if ($docBlock = $method->getDocComment()) {
            $callees = array_merge($callees, $this->readDocBlockCallees($class, $method, $docBlock));
        }

        return $callees;
    }