code: func (a *HistoricalApi) availableFreeContainerMetrics(request *restful.Request, response *restful.Response) {
  	key := core.HistoricalKey{
  		ObjectType:    core.MetricSetTypeSystemContainer,
  		NodeName:      request.PathParameter("node-name"),
  		ContainerName: request.PathParameter("container-name"),
  	}
  	a.processMetricNamesRequest(key, response)
  }
docs: // availableFreeContainerMetrics returns a list of available pod metric names.