public Map<byte[], List<Path>> bulkLoadHFiles(Collection<Pair<byte[], String>> familyPaths,
    boolean assignSeqId, BulkLoadListener bulkLoadListener) throws IOException {
    return bulkLoadHFiles(familyPaths, assignSeqId, bulkLoadListener, false, null, true);
  }
Attempts to atomically load a group of hfiles. This is critical for loading rows with multiple
column families atomically.
@param familyPaths      List of Pair&lt;byte[] column family, String hfilePath&gt;
@param bulkLoadListener Internal hooks enabling massaging/preparation of a file about to be
                        bulk loaded
@return Map from family to List of store file paths if successful, null if failed recoverably
@throws IOException if failed unrecoverably.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java