import com.google.common.base.Verify;
import java.util.ArrayDeque;
import java.util.Optional;
import com.google.common.base.Verify;
import java.util.ArrayDeque;
import java.util.Optional;
private RequestException previousFailure;
FrontendTransaction(final AbstractFrontendHistory history, final TransactionIdentifier id) {
private RequestException previousFailure;
FrontendTransaction(final AbstractFrontendHistory history, final TransactionIdentifier id) {