code: func (i *btreeItem) Less(iother btree.Item) bool {
  	switch other := iother.(type) {
  	case *btreeItem:
  		return bytes.Compare(i.Key, other.Key) < 0
  	case *prefixItem:
  		return !iother.Less(i)
  	default:
  		return false
  	}
  }
docs: // Less is used for Btree operations,
  // returns true if item is less than the other one