code: public void bindToFileSystem(GoogleHadoopFileSystemBase fs, Text service) {
      this.fileSystem = requireNonNull(fs);
      this.service = requireNonNull(service);
    }
docs: Bind to the filesystem. Subclasses can use this to perform their own binding operations - but
  they must always call their superclass implementation. This <i>Must</i> be called before
  calling {@code init()}.
  
  <p><b>Important:</b> This binding will happen during FileSystem.initialize(); the FS is not
  live for actual use and will not yet have interacted with GCS services.
  
  @param fs owning FS.
  @param service name of the service (i.e. bucket name) for the FS.