public static ExpressionOperator copyOperator(final ExpressionOperator operator) {
        if (operator == null) {
            return null;
        }

        final ExpressionOperator.Builder builder = ExpressionOperator
                .builder()
                .enabled(operator.getEnabled())
                .op(operator.getOp());
        if (operator.getChildren() != null) {
            operator.getChildren().forEach(item -> {
                if (item instanceof ExpressionOperator) {
                    builder.addOperator(copyOperator((ExpressionOperator) item));

                } else if (item instanceof ExpressionTerm) {
                    builder.addTerm(copyTerm((ExpressionTerm) item));
                }
            });
        }
        return builder.build();
    }
@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