code: func (cst *ClientSessionTransport) Copy(ctx context.Context, id fscache.RemoteIdentifier, dest string, cu filesync.CacheUpdater) error {
  	csi, ok := id.(*ClientSessionSourceIdentifier)
  	if !ok {
  		return errors.New("invalid identifier for client session")
  	}
  
  	return filesync.FSSync(ctx, csi.caller, filesync.FSSendRequestOpt{
  		IncludePatterns: csi.includePatterns,
  		DestDir:         dest,
  		CacheUpdater:    cu,
  	})
  }
docs: // Copy data from a remote to a destination directory.