import akka.dispatch.OnComplete;
import akka.pattern.Patterns;
import akka.util.Timeout;
-import com.google.common.base.Optional;
import com.google.common.base.Throwables;
import com.google.common.collect.ClassToInstanceMap;
import com.google.common.collect.ForwardingObject;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
+import java.util.Optional;
import java.util.Set;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.ExecutionException;