@Override
  public synchronized void addDataset(Dataset dataset) {
    String accountName = dataset.getAccountName();
    String containerName = dataset.getContainerName();
    nameToDatasetMap.putIfAbsent(new Pair<>(accountName, containerName), new HashMap<>());
    nameToDatasetMap.get(new Pair<>(accountName, containerName)).put(dataset.getDatasetName(), dataset);
  }
Constructor.
@param shouldReturnOnlyUnknown {@code true} if always returns {@link InMemAccountService#UNKNOWN_ACCOUNT} when queried
                                                    by account name; {@code false} to do the actual query.
@param notifyConsumers {@code true} if consumers should be notified of account changes. {@code false} otherwise.
ambry-test-utils/src/main/java/com/github/ambry/account/InMemAccountService.java