code: func (l *ItemList) PushFrontList(other *ItemList) {
  	l.lazyInit()
  	for i, e := other.Len(), other.Back(); i > 0; i, e = i-1, e.Prev() {
  		l.insertValue(e.Value, &l.root)
  	}
  }
docs: // PushFrontList inserts a copy of an other list at the front of list l.
  // The lists l and other may be the same. They must not be nil.