New interface definitions and how to know if it's update, delete, create etc

Hi everyone,

I’m new to the community and did create a new interface template (https://github.com/hagbard-01/vyos-1x/blob/current/interface-definitions/beep-on-boot.xml), so far so good.
The template will render a node.def which calls either enable or disable for a systemd unit.
However I realized, that delete comes into play as well, so I need to implement an action for ‘delete system options beep-if-fully-booted’ too, which then calls ‘systemctl -q disable beep’.
According to the conversion table, that needs to be handled then via ascript, so I created a script but how do I know that the script call is create, delete or update etc.?

Any help appreciated.
-h