Sonar Plugin - erb front end - displaying property map by key

Sonar Plugin - erb front end - displaying property map by key

I am sure there is a way to do this, but cannot seem to figure out how to
access a Sonar property by key.
Lets say I have a metric that I built using:
PropertiesBuilder.build()
This creates a map.
I load the map on the ruby side:
How do I access the mymap.get('key') on the ruby side?
thanks!