apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/service/NamespaceService.java/NamespaceService/findParentNamespace
class NamespaceService:  public Namespace findParentNamespace(String appId, String clusterName, String namespaceName) {
    return findParentNamespace(new Namespace(appId, clusterName, namespaceName));
  }