public function findNodes($message_type, $ask)
    {
        $nodes = Node::findByTypeAndPattern($message_type, $ask);

        if ($nodes->count() === 0) {
            $nodes = Node::findByTypeAndPattern('default');
        }

        return $nodes->filter(function ($node) {
            $pageId = Conversation::get('page_id');

            return (empty($node['sources']) || (isset($node->sources['global']) && $node->sources['global'] == true)
                || (isset($node->sources[$pageId]) && $node->sources[$pageId] == true));
        });
    }