code: func (cs *ChangesSync) AppendResourceInstanceChange(changeSrc *ResourceInstanceChangeSrc) {
  	if cs == nil {
  		panic("AppendResourceInstanceChange on nil ChangesSync")
  	}
  	cs.lock.Lock()
  	defer cs.lock.Unlock()
  
  	s := changeSrc.DeepCopy()
  	cs.changes.Resources = append(cs.changes.Resources, s)
  }
docs: // AppendResourceInstanceChange records the given resource instance change in
  // the set of planned resource changes.
  //
  // The caller must ensure that there are no concurrent writes to the given
  // change while this method is running, but it is safe to resume mutating
  // it after this method returns without affecting the saved change.