code: func (c *RefCount) Finalize() {
  	n := c.NumRef()
  	tracebackEvent(c, n, finalizeEvent)
  
  	if n != 0 {
  		err := fmt.Errorf("finalize before zero ref count, ref=%d", n)
  		panicRef(c, err)
  	}
  
  	if f := c.Finalizer(); f != nil {
  		f.Finalize()
  	}
  }
docs: // Finalize will call the finalizer if any, ref count must be zero.