code: func (h *hawkularSink) updateDefinitions(mds []*metrics.MetricDefinition) error {
  	for _, p := range mds {
  		if model, f := h.models[p.Tags[descriptorTag]]; f && !h.recent(p, model) {
  			if err := h.client.UpdateTags(p.Type, p.ID, p.Tags, h.modifiers...); err != nil {
  				return err
  			}
  		}
  		h.cache(p)
  	}
  
  	return nil
  }
docs: // Fetches definitions from the server and checks that they're matching the descriptors