public function getTokens($string)
    {
        $tokens      = [];
        $scanResults = $this->engine->getTokenizer()->scan($string);

        foreach ($scanResults as $scanResult) {
            if (
                isset($scanResult['type'])
                && isset($scanResult['name'])
                && \Mustache_Tokenizer::T_ESCAPED === $scanResult['type']
            ) {
                $tokens[$scanResult['name']] = true;
            }
        }

        return array_keys($tokens);
    }