public List<String> getLastNRequestedPartitionClasses() {
    return lastRequestedPartitionClasses;
  }
@return the partition classes requested for in the late N calls to {@link #getAllPartitionIds(String)} or
{@link #getWritablePartitionIds(String)}.
ambry-test-utils/src/main/java/com/github/ambry/clustermap/MockClusterMap.java