code: func (d *Driver) Put(id string) error {
  	mountpoint := d.mountPath(id)
  	if count := d.ctr.Decrement(mountpoint); count > 0 {
  		return nil
  	}
  
  	logger := logrus.WithField("storage-driver", "zfs")
  
  	logger.Debugf(`unmount("%s")`, mountpoint)
  
  	if err := unix.Unmount(mountpoint, unix.MNT_DETACH); err != nil {
  		logger.Warnf("Failed to unmount %s mount %s: %v", id, mountpoint, err)
  	}
  	if err := unix.Rmdir(mountpoint); err != nil && !os.IsNotExist(err) {
  		logger.Debugf("Failed to remove %s mount point %s: %v", id, mountpoint, err)
  	}
  
  	return nil
  }
docs: // Put removes the existing mountpoint for the given id if it exists.