code: func GetOldReplicaSets(deployment extensions.Deployment, c clientset.Interface) ([]*extensions.ReplicaSet, []*extensions.ReplicaSet, error) {
  	return GetOldReplicaSetsFromLists(deployment, c,
  		func(namespace string, options api.ListOptions) (*api.PodList, error) {
  			return c.Core().Pods(namespace).List(options)
  		},
  		func(namespace string, options api.ListOptions) ([]extensions.ReplicaSet, error) {
  			rsList, err := c.Extensions().ReplicaSets(namespace).List(options)
  			return rsList.Items, err
  		})
  }
docs: // GetOldReplicaSets returns the old replica sets targeted by the given Deployment; get PodList and ReplicaSetList from client interface.
  // Note that the first set of old replica sets doesn't include the ones with no pods, and the second set of old replica sets include all old replica sets.