code: func Register(component, version string) {
  	registry.m.Lock()
  	defer registry.m.Unlock()
  	if registry.r == nil {
  		registry.r = make(map[string]string, 1)
  	}
  	registry.r[component] = version
  }
docs: // Register tells the library to start reporting a version for given component.
  //
  // This should usually called during 'init' time.
  //
  // The component name will be used as a value of 'component' metric field, and
  // the given version will become the actual reported metric value. It is a good
  // idea to use a fully qualified go package name as 'component'.