class AbstractMetricGroup implements MetricGroup {

	public Map<String, String> getAllVariables() {
		if (variables == null) {
			Map<String, String> tmpVariables = new HashMap<>();
			putVariables(tmpVariables);
			if (parent != null) { // not true for Job-/TaskManagerMetricGroup
				tmpVariables.putAll(parent.getAllVariables());
			}
			variables = tmpVariables;
		}
		return variables;
	}

	public  AbstractMetricGroup(MetricRegistry registry, String[] scope, A parent);

}