code: func (k *KV) DeleteCAS(p *KVPair, q *WriteOptions) (bool, *WriteMeta, error) {
  	params := map[string]string{
  		"cas": strconv.FormatUint(p.ModifyIndex, 10),
  	}
  	return k.deleteInternal(p.Key, params, q)
  }
docs: // DeleteCAS is used for a Delete Check-And-Set operation. The Key
  // and ModifyIndex are respected. Returns true on success or false on failures.