protected function fixServices(array &$definitions)
    {
        foreach ($definitions as $id => $def) {
            if (is_array($def)) {
                if (!isset($def['class'])) {
                    $def = ['class' => $def];
                } elseif (!is_array($def['class'])) {
                    $def['class'] = [ $def['class'] ];
                }
            } else {
                $def = ['class' => [ $def ]];
            }
            $definitions[$id] = $def;
        }
    }