code: public static Expression map(String operator, Val<Expression> arg, QueryExprMeta parent) {
          if (parent == null) {
              throw new QuerySyntaxException(Messages.get("dsl.arguments.error5", operator));
          } else if (!parent.operator().equals("option")) {
              throw new QuerySyntaxException(Messages.get("dsl.arguments.error6", operator, "option"));
          }
          return MapExpression.of(operator, arg);
      }
docs: <p>map.</p>
  
  @param operator a {@link java.lang.String} object.
  @param arg a {@link ameba.db.dsl.QueryExprMeta.Val} object.
  @param parent a {@link ameba.db.dsl.QueryExprMeta} object.
  @return a {@link io.ebean.Expression} object.