I needed to add NULL as a string in my script for liquibase xml

I needed to add NULL as a string in my script for liquibase xml, how can I do that?
Below is the code:

nullAsStringValue attribute is not working neither does these \NULL\ or any combination like this, please suggest a solution

Could this be related to this open Pull Request? After liquibase upgrade 3.5 -> 4.5 loadData with null values for string/varchar type columns fails · Issue #2177 · liquibase/liquibase · GitHub