Writing new value to global tag with pipeline script block

I’m sure this is simple but I’m new in the scripting realm so I’m not sure which function of the alarm pipeline “event” to call in order to get the source path of an alarm event. I would like to write to a different tag or property in the tag that alarmed.

The alarm trigger would come from the path:
and I would like a value write to the tag
[default]tagName{Area} if we can actually set a tag property with this expression block.

I assumed it would be something like this:

fullTagPath = event.source.SourcePath???
pathForPipeline = fullTagPath.split("/")[:-2]
pathForPipeline = “/”.join(tagPath)

This pathForPipeline will be used in:

system.tag.write(pathForPipeline, “area1”)

Any help for this is greatly appreciated.