public function getWriterClassNameByFormat($format)
    {
        $format = strtolower($format);
        foreach ($this->writers as $writer) {
            $class = get_class($writer);
            $name  = strtolower(substr($class, strrpos($class, '\\') + 1));

            if ($name == $format) {
                return $class;
            }
        }

        return null;
    }