code: func (c *Conn) RemoveBulk(keys []string) (int64, error) {
  	vals := make([]KV, 0, len(keys))
  	for _, k := range keys {
  		vals = append(vals, KV{"_" + k, zeroslice})
  	}
  	code, m, err := c.doRPC("/rpc/remove_bulk", vals)
  	if err != nil {
  		return 0, err
  	}
  	if code != 200 {
  		return 0, makeError(m)
  	}
  	return strconv.ParseInt(string(findRec(m, "num").Value), 10, 64)
  }
docs: // RemoveBulk deletes the values