def METHOD_NAME(identifier):
  choice = os.getenv("FB_FS")
  if choice == "testing":
    path = os.path.join(get_build_dir(), "fs")
    if not os.path.isdir(path):
      LOG.warning(("Could not find fs directory: %s. Perhaps you need to run manage.py filebrowser_test_setup?") % path)
    return LocalSubFileSystem(path)
  else:
    cluster_conf = conf.HDFS_CLUSTERS[identifier]
    return webhdfs.WebHdfs.from_config(cluster_conf)