### my timeseries is like

mail_elapsed{group="prod", domain="foo.it", program="postfix", job="mtail"} = 12
mail_elapsed{group="prod", domain="bar.it", program="postfix", job="mtail"} = 321
mail_elapsed{group="prod", domain="smurf.it", program="postfix", job="mtail"} = 11231
mail_elapsed{group="prod", domain="boo.it", program="postfix", job="mtail"} = 14


### I expect grafana

-  to show only relevant data in the legend

mail_elapsed{domain="foo.it"} = 12
mail_elapsed{domain="bar.it"} = 321
mail_elapsed{domain="smurf.it"} = 11231
mail_elapsed{domain="boo.it"} = 14

### I do it via

drop_common_labels(mail_elapsed{group="prod"})