default String parseSfString(String value) {
        if (value == null) {
            return null;
        }
        Matcher matcher = SF_STRING_PATTERN.matcher(value);
        if (matcher.find()) {
            String result = matcher.group(1).trim();
            if (result.isEmpty()) {
                return null;
            }
            return result;
        }
        return null;
    }
A sf-string is a String with '"' around it.

@param value The value to be parsed
@return The actual payload string (i.e. without the surrounding '"') or null if invalid
analyzer/src/main/java/nl/basjes/parse/useragent/clienthints/parsers/CHParser.java