void checkBack() {
        for (LevelController ctrl : levelControllerMap.values()) {
            ctrl.checkBack();
        }
    }
Contains a repository of mapped log level controllers.

@author Ulf Lilleengen
@since 5.1
Should only be used internally in the log library
vespalog/src/main/java/com/yahoo/log/MappedLevelControllerRepo.java