code: @SuppressWarnings("unchecked")
      @Override
      protected Val<Expression> expr(String field, String op, Val<Expression>[] args, QueryExprMeta parent) {
          Iterable<ExprTransformer> transformers = getTransformer(ExprTransformer.class);
          for (ExprTransformer<Expression, EbeanExprInvoker> transformer : transformers) {
              Transformed<Val<Expression>> transformed = transformer.transform(field, op, args, this, parent);
              if (transformed.success()) {
                  return transformed.result();
              }
          }
          throw new QuerySyntaxException(Messages.get("dsl.transform.err", field, op, Arrays.toString(args)));
      }
docs: {@inheritDoc}