@Override
    public boolean check(SourceData sourceData, int rowIndex, Context context) {
        Object leftObj = null;
        if (leftParser != null) {
            leftObj = leftParser.parse(sourceData, rowIndex, context);
        } else {
            leftObj = operator.check(sourceData, rowIndex, context);
        }
        if (isNot) {
            return !(leftObj == null);
        } else {
            return leftObj == null;
        }
    }
IsNullOperator ->  expr is [not] null
Description:  expr can accept ValueParser and ExpressionOperation:
return the judgment result
inlong-sdk/transform-sdk/src/main/java/org/apache/inlong/sdk/transform/process/operator/IsNullOperator.java