public static List<String> values(final ExpressionOperator expressionOperator, final String fieldName) {
        return terms(expressionOperator,
                Collections.singleton(fieldName)).stream().map(ExpressionTerm::getValue).collect(
                Collectors.toList());
    }
@return True if there are at least one enabled term under the expressionOperator
stroom-query/stroom-query-api/src/main/java/stroom/query/api/ExpressionUtil.java