docs: static List<String> sanitiseAndSplit(final String param) {
          if (Strings.isNullOrEmpty(param)) return ImmutableList.of();
          // sanitize the user input, only keep letters, digits, and any of a small number of approved params
          final String sanitized = JAVA_LETTER_OR_DIGIT.or(anyOf(".,_-[]")).retainFrom(param);
          return Splitter.on(',').trimResults().omitEmptyStrings().splitToList(sanitized);
      }