code: func (s *APIServer) getNodes(auth ClientI, w http.ResponseWriter, r *http.Request, p httprouter.Params, version string) (interface{}, error) {
  	namespace := p.ByName("namespace")
  	if !services.IsValidNamespace(namespace) {
  		return nil, trace.BadParameter("invalid namespace %q", namespace)
  	}
  	skipValidation, _, err := httplib.ParseBool(r.URL.Query(), "skip_validation")
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	var opts []services.MarshalOption
  	if skipValidation {
  		opts = append(opts, services.SkipValidation())
  	}
  
  	servers, err := auth.GetNodes(namespace, opts...)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	return marshalServers(servers, version)
  }
docs: // getNodes returns registered SSH nodes