code: func (c *photonPersistentDiskUnmounter) TearDown() error {
  	err := c.TearDownAt(c.GetPath())
  	if err != nil {
  		return err
  	}
  
  	removeFromScsiSubsystem(c.volName)
  	return nil
  }
docs: // Unmounts the bind mount, and detaches the disk only if the PD
  // resource was the last reference to that disk on the kubelet.