public Selector offset(Constant constant) {

        if (constant instanceof IntConstant || constant instanceof LongConstant) {
            offset = constant;
            return this;
        } else {
            throw new UnsupportedAttributeTypeException("'offset' only supports int or long constants, but found '" +
                    constant + "'");
        }
    }
Selector selecting query output stream attributes
modules/siddhi-query-api/src/main/java/io/siddhi/query/api/execution/query/selection/Selector.java