@Override
    public Object parse(SourceData sourceData, int rowIndex, Context context) {
        Object val = null;
        try {
            if (stringParser != null) {
                val = stringParser.parse(sourceData, rowIndex, context);
            } else {
                val = operator.check(sourceData, rowIndex, context);
            }
        } catch (Exception ignored) {

        }
        return val == null;
    }
IsNullFunction  -> isnull(expr)
description:
- return true if expr is NULL
- return false otherwise.
inlong-sdk/transform-sdk/src/main/java/org/apache/inlong/sdk/transform/process/function/condition/IsNullFunction.java