code: func NewListIndex(parent *bolt.Bucket, indexName []byte) (*ListIndex, error) {
  	var err error
  	b := parent.Bucket(indexName)
  	if b == nil {
  		if !parent.Writable() {
  			return nil, ErrNotFound
  		}
  		b, err = parent.CreateBucket(indexName)
  		if err != nil {
  			return nil, err
  		}
  	}
  
  	ids, err := NewUniqueIndex(b, []byte("storm__ids"))
  	if err != nil {
  		return nil, err
  	}
  
  	return &ListIndex{
  		IndexBucket: b,
  		Parent:      parent,
  		IDs:         ids,
  	}, nil
  }
docs: // NewListIndex loads a ListIndex