code: public final void rollback(String database, ByteString transaction) {
  
      RollbackRequest request =
          RollbackRequest.newBuilder().setDatabase(database).setTransaction(transaction).build();
      rollback(request);
    }
docs: Rolls back a transaction.
  
  <p>Sample code:
  
  <pre><code>
  try (FirestoreClient firestoreClient = FirestoreClient.create()) {
  String formattedDatabase = DatabaseRootName.format("[PROJECT]", "[DATABASE]");
  ByteString transaction = ByteString.copyFromUtf8("");
  firestoreClient.rollback(formattedDatabase, transaction);
  }
  </code></pre>
  
  @param database The database name. In the format:
  `projects/{project_id}/databases/{database_id}`.
  @param transaction The transaction to roll back.
  @throws com.google.api.gax.rpc.ApiException if the remote call fails