code: public static COSUnderFileSystem createInstance(AlluxioURI uri, UnderFileSystemConfiguration conf,
        AlluxioConfiguration alluxioConf)
        throws Exception {
      String bucketName = UnderFileSystemUtils.getBucketName(uri);
      Preconditions.checkArgument(conf.isSet(PropertyKey.COS_ACCESS_KEY),
          "Property %s is required to connect to COS", PropertyKey.COS_ACCESS_KEY);
      Preconditions.checkArgument(conf.isSet(PropertyKey.COS_SECRET_KEY),
          "Property %s is required to connect to COS", PropertyKey.COS_SECRET_KEY);
      Preconditions.checkArgument(conf.isSet(PropertyKey.COS_REGION),
          "Property %s is required to connect to COS", PropertyKey.COS_REGION);
      Preconditions.checkArgument(conf.isSet(PropertyKey.COS_APP_ID),
          "Property %s is required to connect to COS", PropertyKey.COS_APP_ID);
      String accessKey = conf.get(PropertyKey.COS_ACCESS_KEY);
      String secretKey = conf.get(PropertyKey.COS_SECRET_KEY);
      String regionName = conf.get(PropertyKey.COS_REGION);
      String appId = conf.get(PropertyKey.COS_APP_ID);
  
      COSCredentials cred = new BasicCOSCredentials(accessKey, secretKey);
      ClientConfig clientConfig = createCOSClientConfig(regionName, conf);
      COSClient client = new COSClient(cred, clientConfig);
  
      return new COSUnderFileSystem(uri, client, bucketName, appId, conf, alluxioConf);
    }
docs: Constructs a new instance of {@link COSUnderFileSystem}.
  
  @param uri the {@link AlluxioURI} for this UFS
  @param conf the configuration for this UFS
  @param alluxioConf Alluxio configuration
  @return the created {@link COSUnderFileSystem} instance