import akka.dispatch.Mapper;
import akka.dispatch.OnComplete;
import akka.util.Timeout;
-import com.google.common.base.Optional;
import java.util.Collection;
+import java.util.Optional;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.ConcurrentHashMap;
import org.opendaylight.controller.cluster.datastore.exceptions.LocalShardNotFoundException;