// This is a JSON object type (that preserves key order)
			kvs, ok := mv.Value.(jstream.KVS)
			if ok {
				for _, kv := range kvs {
					if sset.Contains(kv.Key) {
						// Reject duplicate conditions or expiration.
						return nil, fmt.Errorf("input policy has multiple %s, please fix your client code", kv.Key)
					}
					sset.Add(kv.Key)
				}
			}
			e.Encode(kvs)
		}
	}
	return &buf, d.Err()
}