code: private void injectTagsToEvent(GobblinTrackingEvent event) {
      Map<String, String> originalMetadata = event.getMetadata();
      Map<String, Object> tags = getTagMap();
      Map<String, String> newMetadata = Maps.newHashMap();
      for(Map.Entry<String, Object> entry : tags.entrySet()) {
        newMetadata.put(entry.getKey(), entry.getValue().toString());
      }
      newMetadata.putAll(originalMetadata);
      event.setMetadata(newMetadata);
    }
docs: Inject the tags of this {@link MetricContext} to the given {@link GobblinTrackingEvent}