code: func (f *Frame) Drop() {
  	if f.Len() == 0 {
  		return
  	}
  
  	top := f.Len() - 1
  	f.stack[top] = nil
  	f.stack = f.stack[:top]
  }
docs: // Drop extracts the noder with the alphabetically smaller name in the
  // frame or does nothing if the frame was empty.