public static function parseTokens(array $tokens, $prefix = '', $postfix = '')
    {
        $parsedTokens = array();
        foreach (self::$tokenNames as $name) {
            $key = $prefix . $name . $postfix;
            if (isset($tokens[$key])) {
                $parsedTokens[$name] = new self($name, $tokens[$key]);
            }
        }
        return $parsedTokens;
    }