I tried to shorten the output by defining the css prefix as 'ac', but realized that it will never work due to the fact that the converter has ansi_color_ hardcoded and there is no connection between the Theme and the Converter.

$converter = new AnsiToHtmlConverter();
$converter->convert('some random cli output'); // returns classes with "ansi_color" prefix
$converter->getTheme()->asCss('css_prefix_for_ansi_color'); // returns styles with given prefix