code: protected IntObjectOpenHashMap<ArrayList<byte[]>> getBucketKeyMapping(byte[]... keys) {
          IntObjectOpenHashMap<ArrayList<byte[]>> bucketKeyMapping = new IntObjectOpenHashMap<ArrayList<byte[]>>();
          int bucketId;
          for (byte[] key : keys) {
              bucketId = hashFunction.getBucketId(key);
              if (!bucketKeyMapping.containsKey(bucketId)) {
                  bucketKeyMapping.put(bucketId, new ArrayList<byte[]>());
              }
              bucketKeyMapping.get(bucketId).add(key);
          }
          return bucketKeyMapping;
      }
docs: This method maps all keys in the given array to their corresponding buckets and returns the determined mapping.
  
  @param keys
  the keys to search for
  @return a mapping from bucket-id to a list of keys.