key value must belong to a identical label, a labels is equivalent to a map, it is represent as a json object
{ "app": "some_app", "service": "payment", "environment": "production", "version": "1.0.1" }
A key is usually related to some function in your program, let's say a new web UI should enable or not. the labels is just like a map to tell you where this program located in. the map says, it is located in production environment,the version is 1.0.1
{ "value":"true", "labels":{ "service": "web-console", "environment": "production", "version": "1.0.1" } }