protected Map<DataNodeId, List<RemoteReplicaInfo>> selectReplicas(Map<DataNodeId, List<RemoteReplicaInfo>> replicas) {
    // custom filter that inheritors can override for various use cases
    return replicas;
  }
A custom filter that inheritors can override depending upon use case to pick which replicas to replicate from
@param replicas A map of replicas {host -> {replicas}}
ambry-replication/src/main/java/com/github/ambry/replication/ReplicaThread.java