@Override
    public Object parse(SourceData sourceData, int rowIndex, Context context) {
        Object stringObj = stringParser.parse(sourceData, rowIndex, context);
        Object lengthObj = lengthParser.parse(sourceData, rowIndex, context);
        if (stringObj == null || lengthObj == null) {
            return null;
        }
        String str = OperatorTools.parseString(stringObj);
        int len = Integer.parseInt(OperatorTools.parseString(lengthObj));
        if (len <= 0) {
            return "";
        }
        return str.substring(0, Math.min(str.length(), len));
    }
LeftFunction  ->  left(string,length)
description:
- return null if either string or length is null
- return "" if it is less than or equal to zero
- return a substring of length starting from the right side of the string.
inlong-sdk/transform-sdk/src/main/java/org/apache/inlong/sdk/transform/process/function/string/LeftFunction.java