public StatTrackingEventListener appendTags(Map<String,String> newTags){
  if (newTags == null || newTags.isEmpty()) {
    return this;
  }
  if (tags == null) {
    tags=Maps.newLinkedHashMap();
  }
  tags.putAll(newTags);
  return this;
}

public StatTrackingEventListener appendTags ( Map < String , String > newTags ) { if ( newTags == null || newTags . isEmpty ( ) ) { return this ; } if ( tags == null ) { tags = Maps . newLinkedHashMap ( ) ; } tags . putAll ( newTags ) ; return this ; }
append a map of tag names and tag values to the end of the tags string . the tags string will be attached onto counters / metrics
