How to use the datastore-core.TieredDatastore function in datastore-core

const peerId = ipfs._peerInfo.id

    pubsubDs = new PubsubDatastore(pubsub, localDatastore, peerId)
    ipnsStores.push(pubsubDs)
  }

  // DHT should not be added as routing if we are offline or it is disabled
  if (get(ipfs._options, 'offline') || !get(ipfs._options, 'libp2p.config.dht.enabled', false)) {
    const offlineDatastore = new OfflineDatastore(ipfs._repo)
    ipnsStores.push(offlineDatastore)
  } else {
    ipnsStores.push(ipfs.libp2p.dht)
  }

  // Create ipns routing with a set of datastores
  return new TieredDatastore(ipnsStores)
}