public function getSupportedInputFormats(string $given_output_format): array
    {
        $result = [];
        foreach ($this->converters as $formats) {
            list($input_format, $output_format) = $formats;
            if ($given_output_format === $output_format) {
                $result[] = $input_format;
            }
        }

        return $result;
    }