public TopNMetric(TopNMetricType type,String previousStop){
  this.type=type;
  this.metricName=Optional.empty();
  this.nested=Optional.empty();
  this.previousStop=Optional.of(previousStop);
}

public TopNMetric ( TopNMetricType type , String previousStop ) { this . type = type ; this . metricName = Optional . empty ( ) ; this . nested = Optional . empty ( ) ; this . previousStop = Optional . of ( previousStop ) ; }
constructs a sort of the given type with a starting point .
