import com.google.common.util.concurrent.Futures;
import java.util.Collections;
import java.util.Set;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.Executor;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.TimeoutException;
import javax.annotation.Nullable;
import org.opendaylight.controller.netconf.api.NetconfMessage;