code: func (c *index) Drop(rm kv.RetrieverMutator) error {
  	it, err := rm.Iter(c.prefix, c.prefix.PrefixNext())
  	if err != nil {
  		return err
  	}
  	defer it.Close()
  
  	// remove all indices
  	for it.Valid() {
  		if !it.Key().HasPrefix(c.prefix) {
  			break
  		}
  		err := rm.Delete(it.Key())
  		if err != nil {
  			return err
  		}
  		err = it.Next()
  		if err != nil {
  			return err
  		}
  	}
  	return nil
  }
docs: // Drop removes the KV index from store.