apollo-openapi/src/main/java/com/ctrip/framework/apollo/openapi/client/ApolloOpenApiClient.java/ApolloOpenApiClient/getNamespaces
class ApolloOpenApiClient:  public List<OpenNamespaceDTO> getNamespaces(String appId, String env, String clusterName) {
    return namespaceService.getNamespaces(appId, env, clusterName);
  }